<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/net/core/skbuff.c, branch linux-6.6.y</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>net: skbuff: propagate shared-frag marker through frag-transfer helpers</title>
<updated>2026-05-23T11:03:36+00:00</updated>
<author>
<name>Hyunwoo Kim</name>
<email>imv4bel@gmail.com</email>
</author>
<published>2026-05-15T22:28:53+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=989214c66884d70716d83dc1d0bf5e16287bf349'/>
<id>989214c66884d70716d83dc1d0bf5e16287bf349</id>
<content type='text'>
commit 48f6a5356a33dd78e7144ae1faef95ffc990aae0 upstream.

Two frag-transfer helpers (__pskb_copy_fclone() and skb_shift()) fail
to propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()-&gt;flags when
moving frags from source to destination.  __pskb_copy_fclone() defers
the rest of the shinfo metadata to skb_copy_header() after copying
frag descriptors, but that helper only carries over gso_{size,segs,
type} and never touches skb_shinfo()-&gt;flags; skb_shift() moves frag
descriptors directly and leaves flags untouched.  As a result, the
destination skb keeps a reference to the same externally-owned or
page-cache-backed pages while reporting skb_has_shared_frag() as
false.

The mismatch is harmful in any in-place writer that uses
skb_has_shared_frag() to decide whether shared pages must be detoured
through skb_cow_data().  ESP input is one such writer (esp4.c,
esp6.c), and a single nft 'dup to &lt;local&gt;' rule -- or any other
nf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d
skb in esp_input() with the marker stripped, letting an unprivileged
user write into the page cache of a root-owned read-only file via
authencesn-ESN stray writes.

Set SKBFL_SHARED_FRAG on the destination whenever frag descriptors
were actually moved from the source.  skb_copy() and skb_copy_expand()
share skb_copy_header() too but linearize all paged data into freshly
allocated head storage and emerge with nr_frags == 0, so
skb_has_shared_frag() returns false on its own; they need no change.

The same omission exists in skb_gro_receive() and skb_gro_receive_list().
The former moves the incoming skb's frag descriptors into the
accumulator's last sub-skb via two paths (a direct frag-move loop and
the head_frag + memcpy path); the latter chains the incoming skb whole
onto p's frag_list.  Downstream skb_segment() reads only
skb_shinfo(p)-&gt;flags, and skb_segment_list() reuses each sub-skb's
shinfo as the nskb -- both p and lp must carry the marker.

The same omission also exists in tcp_clone_payload(), which builds an
MTU probe skb by moving frag descriptors from skbs on sk_write_queue
into a freshly allocated nskb.  The helper falls into the same family
and warrants the same fix for consistency; no TCP TX-side in-place
writer is currently known to reach a user page through this gap, but
a future consumer depending on the marker would regress silently.

The same omission exists in skb_segment(): the per-iteration flag
merge takes only head_skb's flag, and the inner switch that rebinds
frag_skb to list_skb on head_skb-frags exhaustion does not fold the
new frag_skb's flag into nskb.  Fold frag_skb's flag at both sites
so segments drawing frags from frag_list members carry the marker.

Fixes: cef401de7be8 ("net: fix possible wrong checksum generation")
Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags")
Suggested-by: Sabrina Dubroca &lt;sd@queasysnail.net&gt;
Suggested-by: Sultan Alsawaf &lt;sultan@kerneltoast.com&gt;
Suggested-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
Suggested-by: Lin Ma &lt;malin89@huawei.com&gt;
Suggested-by: Jingguo Tan &lt;tanjingguo@huawei.com&gt;
Suggested-by: Aaron Esau &lt;aaron1esau@gmail.com&gt;
Cc: stable@vger.kernel.org
Signed-off-by: Hyunwoo Kim &lt;imv4bel@gmail.com&gt;
Tested-by: Rajat Gupta &lt;rajat.gupta@oss.qualcomm.com&gt;
Link: https://patch.msgid.link/ageeJfJHwgzmKXbh@v4bel
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
[bwh: Backported to 6.6: skb_gro_receive_list() is in
 net/ipv4/udp_offload.c here]
Signed-off-by: Ben Hutchings &lt;benh@debian.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 48f6a5356a33dd78e7144ae1faef95ffc990aae0 upstream.

Two frag-transfer helpers (__pskb_copy_fclone() and skb_shift()) fail
to propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()-&gt;flags when
moving frags from source to destination.  __pskb_copy_fclone() defers
the rest of the shinfo metadata to skb_copy_header() after copying
frag descriptors, but that helper only carries over gso_{size,segs,
type} and never touches skb_shinfo()-&gt;flags; skb_shift() moves frag
descriptors directly and leaves flags untouched.  As a result, the
destination skb keeps a reference to the same externally-owned or
page-cache-backed pages while reporting skb_has_shared_frag() as
false.

The mismatch is harmful in any in-place writer that uses
skb_has_shared_frag() to decide whether shared pages must be detoured
through skb_cow_data().  ESP input is one such writer (esp4.c,
esp6.c), and a single nft 'dup to &lt;local&gt;' rule -- or any other
nf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d
skb in esp_input() with the marker stripped, letting an unprivileged
user write into the page cache of a root-owned read-only file via
authencesn-ESN stray writes.

Set SKBFL_SHARED_FRAG on the destination whenever frag descriptors
were actually moved from the source.  skb_copy() and skb_copy_expand()
share skb_copy_header() too but linearize all paged data into freshly
allocated head storage and emerge with nr_frags == 0, so
skb_has_shared_frag() returns false on its own; they need no change.

The same omission exists in skb_gro_receive() and skb_gro_receive_list().
The former moves the incoming skb's frag descriptors into the
accumulator's last sub-skb via two paths (a direct frag-move loop and
the head_frag + memcpy path); the latter chains the incoming skb whole
onto p's frag_list.  Downstream skb_segment() reads only
skb_shinfo(p)-&gt;flags, and skb_segment_list() reuses each sub-skb's
shinfo as the nskb -- both p and lp must carry the marker.

The same omission also exists in tcp_clone_payload(), which builds an
MTU probe skb by moving frag descriptors from skbs on sk_write_queue
into a freshly allocated nskb.  The helper falls into the same family
and warrants the same fix for consistency; no TCP TX-side in-place
writer is currently known to reach a user page through this gap, but
a future consumer depending on the marker would regress silently.

The same omission exists in skb_segment(): the per-iteration flag
merge takes only head_skb's flag, and the inner switch that rebinds
frag_skb to list_skb on head_skb-frags exhaustion does not fold the
new frag_skb's flag into nskb.  Fold frag_skb's flag at both sites
so segments drawing frags from frag_list members carry the marker.

Fixes: cef401de7be8 ("net: fix possible wrong checksum generation")
Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags")
Suggested-by: Sabrina Dubroca &lt;sd@queasysnail.net&gt;
Suggested-by: Sultan Alsawaf &lt;sultan@kerneltoast.com&gt;
Suggested-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
Suggested-by: Lin Ma &lt;malin89@huawei.com&gt;
Suggested-by: Jingguo Tan &lt;tanjingguo@huawei.com&gt;
Suggested-by: Aaron Esau &lt;aaron1esau@gmail.com&gt;
Cc: stable@vger.kernel.org
Signed-off-by: Hyunwoo Kim &lt;imv4bel@gmail.com&gt;
Tested-by: Rajat Gupta &lt;rajat.gupta@oss.qualcomm.com&gt;
Link: https://patch.msgid.link/ageeJfJHwgzmKXbh@v4bel
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
[bwh: Backported to 6.6: skb_gro_receive_list() is in
 net/ipv4/udp_offload.c here]
Signed-off-by: Ben Hutchings &lt;benh@debian.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: skbuff: preserve shared-frag marker during coalescing</title>
<updated>2026-05-23T11:03:35+00:00</updated>
<author>
<name>William Bowling</name>
<email>vakzz@zellic.io</email>
</author>
<published>2026-05-13T04:16:35+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=78bf6b6bb19541d19fbda6242e7cfe2c682763c0'/>
<id>78bf6b6bb19541d19fbda6242e7cfe2c682763c0</id>
<content type='text'>
commit f84eca5817390257cef78013d0112481c503b4a3 upstream.

skb_try_coalesce() can attach paged frags from @from to @to.  If @from
has SKBFL_SHARED_FRAG set, the resulting @to skb can contain the same
externally-owned or page-cache-backed frags, but the shared-frag marker
is currently lost.

That breaks the invariant relied on by later in-place writers.  In
particular, ESP input checks skb_has_shared_frag() before deciding
whether an uncloned nonlinear skb can skip skb_cow_data().  If TCP
receive coalescing has moved shared frags into an unmarked skb, ESP can
see skb_has_shared_frag() as false and decrypt in place over page-cache
backed frags.

Propagate SKBFL_SHARED_FRAG when skb_try_coalesce() transfers paged
frags.  The tailroom copy path does not need the marker because it copies
bytes into @to's linear data rather than transferring frag descriptors.

Fixes: cef401de7be8 ("net: fix possible wrong checksum generation")
Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags")
Signed-off-by: William Bowling &lt;vakzz@zellic.io&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Tested-by: Jiayuan Chen &lt;jiayuan.chen@linux.dev&gt;
Link: https://patch.msgid.link/20260513041635.1289541-1-vakzz@zellic.io
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit f84eca5817390257cef78013d0112481c503b4a3 upstream.

skb_try_coalesce() can attach paged frags from @from to @to.  If @from
has SKBFL_SHARED_FRAG set, the resulting @to skb can contain the same
externally-owned or page-cache-backed frags, but the shared-frag marker
is currently lost.

That breaks the invariant relied on by later in-place writers.  In
particular, ESP input checks skb_has_shared_frag() before deciding
whether an uncloned nonlinear skb can skip skb_cow_data().  If TCP
receive coalescing has moved shared frags into an unmarked skb, ESP can
see skb_has_shared_frag() as false and decrypt in place over page-cache
backed frags.

Propagate SKBFL_SHARED_FRAG when skb_try_coalesce() transfers paged
frags.  The tailroom copy path does not need the marker because it copies
bytes into @to's linear data rather than transferring frag descriptors.

Fixes: cef401de7be8 ("net: fix possible wrong checksum generation")
Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags")
Signed-off-by: William Bowling &lt;vakzz@zellic.io&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Tested-by: Jiayuan Chen &lt;jiayuan.chen@linux.dev&gt;
Link: https://patch.msgid.link/20260513041635.1289541-1-vakzz@zellic.io
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: skb: fix cross-cache free of KFENCE-allocated skb head</title>
<updated>2026-04-27T13:23:31+00:00</updated>
<author>
<name>Jiayuan Chen</name>
<email>jiayuan.chen@linux.dev</email>
</author>
<published>2026-04-14T12:11:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=128b03ccb2582a643983a48a37fda58df80edbde'/>
<id>128b03ccb2582a643983a48a37fda58df80edbde</id>
<content type='text'>
[ Upstream commit 0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516 ]

SKB_SMALL_HEAD_CACHE_SIZE is intentionally set to a non-power-of-2
value (e.g. 704 on x86_64) to avoid collisions with generic kmalloc
bucket sizes. This ensures that skb_kfree_head() can reliably use
skb_end_offset to distinguish skb heads allocated from
skb_small_head_cache vs. generic kmalloc caches.

However, when KFENCE is enabled, kfence_ksize() returns the exact
requested allocation size instead of the slab bucket size. If a caller
(e.g. bpf_test_init) allocates skb head data via kzalloc() and the
requested size happens to equal SKB_SMALL_HEAD_CACHE_SIZE, then
slab_build_skb() -&gt; ksize() returns that exact value. After subtracting
skb_shared_info overhead, skb_end_offset ends up matching
SKB_SMALL_HEAD_HEADROOM, causing skb_kfree_head() to incorrectly free
the object to skb_small_head_cache instead of back to the original
kmalloc cache, resulting in a slab cross-cache free:

  kmem_cache_free(skbuff_small_head): Wrong slab cache. Expected
  skbuff_small_head but got kmalloc-1k

Fix this by always calling kfree(head) in skb_kfree_head(). This keeps
the free path generic and avoids allocator-specific misclassification
for KFENCE objects.

Fixes: bf9f1baa279f ("net: add dedicated kmem_cache for typical/small skb-&gt;head")
Reported-by: Antonius &lt;antonius@bluedragonsec.com&gt;
Closes: https://lore.kernel.org/netdev/CAK8a0jxC5L5N7hq-DT2_NhUyjBxrPocoiDazzsBk4TGgT1r4-A@mail.gmail.com/
Signed-off-by: Jiayuan Chen &lt;jiayuan.chen@linux.dev&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Link: https://patch.msgid.link/20260403014517.142550-1-jiayuan.chen@linux.dev
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
[ adapted variable names ]
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516 ]

SKB_SMALL_HEAD_CACHE_SIZE is intentionally set to a non-power-of-2
value (e.g. 704 on x86_64) to avoid collisions with generic kmalloc
bucket sizes. This ensures that skb_kfree_head() can reliably use
skb_end_offset to distinguish skb heads allocated from
skb_small_head_cache vs. generic kmalloc caches.

However, when KFENCE is enabled, kfence_ksize() returns the exact
requested allocation size instead of the slab bucket size. If a caller
(e.g. bpf_test_init) allocates skb head data via kzalloc() and the
requested size happens to equal SKB_SMALL_HEAD_CACHE_SIZE, then
slab_build_skb() -&gt; ksize() returns that exact value. After subtracting
skb_shared_info overhead, skb_end_offset ends up matching
SKB_SMALL_HEAD_HEADROOM, causing skb_kfree_head() to incorrectly free
the object to skb_small_head_cache instead of back to the original
kmalloc cache, resulting in a slab cross-cache free:

  kmem_cache_free(skbuff_small_head): Wrong slab cache. Expected
  skbuff_small_head but got kmalloc-1k

Fix this by always calling kfree(head) in skb_kfree_head(). This keeps
the free path generic and avoids allocator-specific misclassification
for KFENCE objects.

Fixes: bf9f1baa279f ("net: add dedicated kmem_cache for typical/small skb-&gt;head")
Reported-by: Antonius &lt;antonius@bluedragonsec.com&gt;
Closes: https://lore.kernel.org/netdev/CAK8a0jxC5L5N7hq-DT2_NhUyjBxrPocoiDazzsBk4TGgT1r4-A@mail.gmail.com/
Signed-off-by: Jiayuan Chen &lt;jiayuan.chen@linux.dev&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Link: https://patch.msgid.link/20260403014517.142550-1-jiayuan.chen@linux.dev
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
[ adapted variable names ]
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: fix memory leak in skb_segment_list for GRO packets</title>
<updated>2026-01-17T15:29:59+00:00</updated>
<author>
<name>Mohammad Heib</name>
<email>mheib@redhat.com</email>
</author>
<published>2026-01-04T21:31:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=88bea149db2057112af3aaf63534b24fab5858ab'/>
<id>88bea149db2057112af3aaf63534b24fab5858ab</id>
<content type='text'>
[ Upstream commit 238e03d0466239410b72294b79494e43d4fabe77 ]

When skb_segment_list() is called during packet forwarding, it handles
packets that were aggregated by the GRO engine.

Historically, the segmentation logic in skb_segment_list assumes that
individual segments are split from a parent SKB and may need to carry
their own socket memory accounting. Accordingly, the code transfers
truesize from the parent to the newly created segments.

Prior to commit ed4cccef64c1 ("gro: fix ownership transfer"), this
truesize subtraction in skb_segment_list() was valid because fragments
still carry a reference to the original socket.

However, commit ed4cccef64c1 ("gro: fix ownership transfer") changed
this behavior by ensuring that fraglist entries are explicitly
orphaned (skb-&gt;sk = NULL) to prevent illegal orphaning later in the
stack. This change meant that the entire socket memory charge remained
with the head SKB, but the corresponding accounting logic in
skb_segment_list() was never updated.

As a result, the current code unconditionally adds each fragment's
truesize to delta_truesize and subtracts it from the parent SKB. Since
the fragments are no longer charged to the socket, this subtraction
results in an effective under-count of memory when the head is freed.
This causes sk_wmem_alloc to remain non-zero, preventing socket
destruction and leading to a persistent memory leak.

The leak can be observed via KMEMLEAK when tearing down the networking
environment:

unreferenced object 0xffff8881e6eb9100 (size 2048):
  comm "ping", pid 6720, jiffies 4295492526
  backtrace:
    kmem_cache_alloc_noprof+0x5c6/0x800
    sk_prot_alloc+0x5b/0x220
    sk_alloc+0x35/0xa00
    inet6_create.part.0+0x303/0x10d0
    __sock_create+0x248/0x640
    __sys_socket+0x11b/0x1d0

Since skb_segment_list() is exclusively used for SKB_GSO_FRAGLIST
packets constructed by GRO, the truesize adjustment is removed.

The call to skb_release_head_state() must be preserved. As documented in
commit cf673ed0e057 ("net: fix fraglist segmentation reference count
leak"), it is still required to correctly drop references to SKB
extensions that may be overwritten during __copy_skb_header().

Fixes: ed4cccef64c1 ("gro: fix ownership transfer")
Signed-off-by: Mohammad Heib &lt;mheib@redhat.com&gt;
Reviewed-by: Willem de Bruijn &lt;willemb@google.com&gt;
Link: https://patch.msgid.link/20260104213101.352887-1-mheib@redhat.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 238e03d0466239410b72294b79494e43d4fabe77 ]

When skb_segment_list() is called during packet forwarding, it handles
packets that were aggregated by the GRO engine.

Historically, the segmentation logic in skb_segment_list assumes that
individual segments are split from a parent SKB and may need to carry
their own socket memory accounting. Accordingly, the code transfers
truesize from the parent to the newly created segments.

Prior to commit ed4cccef64c1 ("gro: fix ownership transfer"), this
truesize subtraction in skb_segment_list() was valid because fragments
still carry a reference to the original socket.

However, commit ed4cccef64c1 ("gro: fix ownership transfer") changed
this behavior by ensuring that fraglist entries are explicitly
orphaned (skb-&gt;sk = NULL) to prevent illegal orphaning later in the
stack. This change meant that the entire socket memory charge remained
with the head SKB, but the corresponding accounting logic in
skb_segment_list() was never updated.

As a result, the current code unconditionally adds each fragment's
truesize to delta_truesize and subtracts it from the parent SKB. Since
the fragments are no longer charged to the socket, this subtraction
results in an effective under-count of memory when the head is freed.
This causes sk_wmem_alloc to remain non-zero, preventing socket
destruction and leading to a persistent memory leak.

The leak can be observed via KMEMLEAK when tearing down the networking
environment:

unreferenced object 0xffff8881e6eb9100 (size 2048):
  comm "ping", pid 6720, jiffies 4295492526
  backtrace:
    kmem_cache_alloc_noprof+0x5c6/0x800
    sk_prot_alloc+0x5b/0x220
    sk_alloc+0x35/0xa00
    inet6_create.part.0+0x303/0x10d0
    __sock_create+0x248/0x640
    __sys_socket+0x11b/0x1d0

Since skb_segment_list() is exclusively used for SKB_GSO_FRAGLIST
packets constructed by GRO, the truesize adjustment is removed.

The call to skb_release_head_state() must be preserved. As documented in
commit cf673ed0e057 ("net: fix fraglist segmentation reference count
leak"), it is still required to correctly drop references to SKB
extensions that may be overwritten during __copy_skb_header().

Fixes: ed4cccef64c1 ("gro: fix ownership transfer")
Signed-off-by: Mohammad Heib &lt;mheib@redhat.com&gt;
Reviewed-by: Willem de Bruijn &lt;willemb@google.com&gt;
Link: https://patch.msgid.link/20260104213101.352887-1-mheib@redhat.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: allow small head cache usage with large MAX_SKB_FRAGS values</title>
<updated>2025-11-24T09:30:05+00:00</updated>
<author>
<name>Paolo Abeni</name>
<email>pabeni@redhat.com</email>
</author>
<published>2025-11-07T01:37:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=ed8a77fee4618facd2a539cad7b7366697b5a575'/>
<id>ed8a77fee4618facd2a539cad7b7366697b5a575</id>
<content type='text'>
[ Upstream commit 14ad6ed30a10afbe91b0749d6378285f4225d482 ]

Sabrina reported the following splat:

    WARNING: CPU: 0 PID: 1 at net/core/dev.c:6935 netif_napi_add_weight_locked+0x8f2/0xba0
    Modules linked in:
    CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc1-net-00092-g011b03359038 #996
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
    RIP: 0010:netif_napi_add_weight_locked+0x8f2/0xba0
    Code: e8 c3 e6 6a fe 48 83 c4 28 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc c7 44 24 10 ff ff ff ff e9 8f fb ff ff e8 9e e6 6a fe &lt;0f&gt; 0b e9 d3 fe ff ff e8 92 e6 6a fe 48 8b 04 24 be ff ff ff ff 48
    RSP: 0000:ffffc9000001fc60 EFLAGS: 00010293
    RAX: 0000000000000000 RBX: ffff88806ce48128 RCX: 1ffff11001664b9e
    RDX: ffff888008f00040 RSI: ffffffff8317ca42 RDI: ffff88800b325cb6
    RBP: ffff88800b325c40 R08: 0000000000000001 R09: ffffed100167502c
    R10: ffff88800b3a8163 R11: 0000000000000000 R12: ffff88800ac1c168
    R13: ffff88800ac1c168 R14: ffff88800ac1c168 R15: 0000000000000007
    FS:  0000000000000000(0000) GS:ffff88806ce00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffff888008201000 CR3: 0000000004c94001 CR4: 0000000000370ef0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    &lt;TASK&gt;
    gro_cells_init+0x1ba/0x270
    xfrm_input_init+0x4b/0x2a0
    xfrm_init+0x38/0x50
    ip_rt_init+0x2d7/0x350
    ip_init+0xf/0x20
    inet_init+0x406/0x590
    do_one_initcall+0x9d/0x2e0
    do_initcalls+0x23b/0x280
    kernel_init_freeable+0x445/0x490
    kernel_init+0x20/0x1d0
    ret_from_fork+0x46/0x80
    ret_from_fork_asm+0x1a/0x30
    &lt;/TASK&gt;
    irq event stamp: 584330
    hardirqs last  enabled at (584338): [&lt;ffffffff8168bf87&gt;] __up_console_sem+0x77/0xb0
    hardirqs last disabled at (584345): [&lt;ffffffff8168bf6c&gt;] __up_console_sem+0x5c/0xb0
    softirqs last  enabled at (583242): [&lt;ffffffff833ee96d&gt;] netlink_insert+0x14d/0x470
    softirqs last disabled at (583754): [&lt;ffffffff8317c8cd&gt;] netif_napi_add_weight_locked+0x77d/0xba0

on kernel built with MAX_SKB_FRAGS=45, where SKB_WITH_OVERHEAD(1024)
is smaller than GRO_MAX_HEAD.

Such built additionally contains the revert of the single page frag cache
so that napi_get_frags() ends up using the page frag allocator, triggering
the splat.

Note that the underlying issue is independent from the mentioned
revert; address it ensuring that the small head cache will fit either TCP
and GRO allocation and updating napi_alloc_skb() and __netdev_alloc_skb()
to select kmalloc() usage for any allocation fitting such cache.

Reported-by: Sabrina Dubroca &lt;sd@queasysnail.net&gt;
Suggested-by: Eric Dumazet &lt;edumazet@google.com&gt;
Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAGS")
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
[ Minor context change fixed. ]
Signed-off-by: Wenshan Lan &lt;jetlan9@163.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 14ad6ed30a10afbe91b0749d6378285f4225d482 ]

Sabrina reported the following splat:

    WARNING: CPU: 0 PID: 1 at net/core/dev.c:6935 netif_napi_add_weight_locked+0x8f2/0xba0
    Modules linked in:
    CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc1-net-00092-g011b03359038 #996
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
    RIP: 0010:netif_napi_add_weight_locked+0x8f2/0xba0
    Code: e8 c3 e6 6a fe 48 83 c4 28 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc c7 44 24 10 ff ff ff ff e9 8f fb ff ff e8 9e e6 6a fe &lt;0f&gt; 0b e9 d3 fe ff ff e8 92 e6 6a fe 48 8b 04 24 be ff ff ff ff 48
    RSP: 0000:ffffc9000001fc60 EFLAGS: 00010293
    RAX: 0000000000000000 RBX: ffff88806ce48128 RCX: 1ffff11001664b9e
    RDX: ffff888008f00040 RSI: ffffffff8317ca42 RDI: ffff88800b325cb6
    RBP: ffff88800b325c40 R08: 0000000000000001 R09: ffffed100167502c
    R10: ffff88800b3a8163 R11: 0000000000000000 R12: ffff88800ac1c168
    R13: ffff88800ac1c168 R14: ffff88800ac1c168 R15: 0000000000000007
    FS:  0000000000000000(0000) GS:ffff88806ce00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffff888008201000 CR3: 0000000004c94001 CR4: 0000000000370ef0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    &lt;TASK&gt;
    gro_cells_init+0x1ba/0x270
    xfrm_input_init+0x4b/0x2a0
    xfrm_init+0x38/0x50
    ip_rt_init+0x2d7/0x350
    ip_init+0xf/0x20
    inet_init+0x406/0x590
    do_one_initcall+0x9d/0x2e0
    do_initcalls+0x23b/0x280
    kernel_init_freeable+0x445/0x490
    kernel_init+0x20/0x1d0
    ret_from_fork+0x46/0x80
    ret_from_fork_asm+0x1a/0x30
    &lt;/TASK&gt;
    irq event stamp: 584330
    hardirqs last  enabled at (584338): [&lt;ffffffff8168bf87&gt;] __up_console_sem+0x77/0xb0
    hardirqs last disabled at (584345): [&lt;ffffffff8168bf6c&gt;] __up_console_sem+0x5c/0xb0
    softirqs last  enabled at (583242): [&lt;ffffffff833ee96d&gt;] netlink_insert+0x14d/0x470
    softirqs last disabled at (583754): [&lt;ffffffff8317c8cd&gt;] netif_napi_add_weight_locked+0x77d/0xba0

on kernel built with MAX_SKB_FRAGS=45, where SKB_WITH_OVERHEAD(1024)
is smaller than GRO_MAX_HEAD.

Such built additionally contains the revert of the single page frag cache
so that napi_get_frags() ends up using the page frag allocator, triggering
the splat.

Note that the underlying issue is independent from the mentioned
revert; address it ensuring that the small head cache will fit either TCP
and GRO allocation and updating napi_alloc_skb() and __netdev_alloc_skb()
to select kmalloc() usage for any allocation fitting such cache.

Reported-by: Sabrina Dubroca &lt;sd@queasysnail.net&gt;
Suggested-by: Eric Dumazet &lt;edumazet@google.com&gt;
Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAGS")
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
[ Minor context change fixed. ]
Signed-off-by: Wenshan Lan &lt;jetlan9@163.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: allow alloc_skb_with_frags() to use MAX_SKB_FRAGS</title>
<updated>2025-10-02T11:42:51+00:00</updated>
<author>
<name>Jason Baron</name>
<email>jbaron@akamai.com</email>
</author>
<published>2025-09-22T19:19:57+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=31ae2fbc9fcb938b798a8f8fb61f6c54b9e79f59'/>
<id>31ae2fbc9fcb938b798a8f8fb61f6c54b9e79f59</id>
<content type='text'>
[ Upstream commit ca9f9cdc4de97d0221100b11224738416696163c ]

Currently, alloc_skb_with_frags() will only fill (MAX_SKB_FRAGS - 1)
slots. I think it should use all MAX_SKB_FRAGS slots, as callers of
alloc_skb_with_frags() will size their allocation of frags based
on MAX_SKB_FRAGS.

This issue was discovered via a test patch that sets 'order' to 0
in alloc_skb_with_frags(), which effectively tests/simulates high
fragmentation. In this case sendmsg() on unix sockets will fail every
time for large allocations. If the PAGE_SIZE is 4K, then data_len will
request 68K or 17 pages, but alloc_skb_with_frags() can only allocate
64K in this case or 16 pages.

Fixes: 09c2c90705bb ("net: allow alloc_skb_with_frags() to allocate bigger packets")
Signed-off-by: Jason Baron &lt;jbaron@akamai.com&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Link: https://patch.msgid.link/20250922191957.2855612-1-jbaron@akamai.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit ca9f9cdc4de97d0221100b11224738416696163c ]

Currently, alloc_skb_with_frags() will only fill (MAX_SKB_FRAGS - 1)
slots. I think it should use all MAX_SKB_FRAGS slots, as callers of
alloc_skb_with_frags() will size their allocation of frags based
on MAX_SKB_FRAGS.

This issue was discovered via a test patch that sets 'order' to 0
in alloc_skb_with_frags(), which effectively tests/simulates high
fragmentation. In this case sendmsg() on unix sockets will fail every
time for large allocations. If the PAGE_SIZE is 4K, then data_len will
request 68K or 17 pages, but alloc_skb_with_frags() can only allocate
64K in this case or 16 pages.

Fixes: 09c2c90705bb ("net: allow alloc_skb_with_frags() to allocate bigger packets")
Signed-off-by: Jason Baron &lt;jbaron@akamai.com&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Link: https://patch.msgid.link/20250922191957.2855612-1-jbaron@akamai.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ipvs: Always clear ipvs_property flag in skb_scrub_packet()</title>
<updated>2025-03-07T15:45:40+00:00</updated>
<author>
<name>Philo Lu</name>
<email>lulie@linux.alibaba.com</email>
</author>
<published>2025-02-22T03:35:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=abdbedfe897469e02dbc9034cffd1fc642831061'/>
<id>abdbedfe897469e02dbc9034cffd1fc642831061</id>
<content type='text'>
[ Upstream commit de2c211868b9424f9aa9b3432c4430825bafb41b ]

We found an issue when using bpf_redirect with ipvs NAT mode after
commit ff70202b2d1a ("dev_forward_skb: do not scrub skb mark within
the same name space"). Particularly, we use bpf_redirect to return
the skb directly back to the netif it comes from, i.e., xnet is
false in skb_scrub_packet(), and then ipvs_property is preserved
and SNAT is skipped in the rx path.

ipvs_property has been already cleared when netns is changed in
commit 2b5ec1a5f973 ("netfilter/ipvs: clear ipvs_property flag when
SKB net namespace changed"). This patch just clears it in spite of
netns.

Fixes: 2b5ec1a5f973 ("netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed")
Signed-off-by: Philo Lu &lt;lulie@linux.alibaba.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Link: https://patch.msgid.link/20250222033518.126087-1-lulie@linux.alibaba.com
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit de2c211868b9424f9aa9b3432c4430825bafb41b ]

We found an issue when using bpf_redirect with ipvs NAT mode after
commit ff70202b2d1a ("dev_forward_skb: do not scrub skb mark within
the same name space"). Particularly, we use bpf_redirect to return
the skb directly back to the netif it comes from, i.e., xnet is
false in skb_scrub_packet(), and then ipvs_property is preserved
and SNAT is skipped in the rx path.

ipvs_property has been already cleared when netns is changed in
commit 2b5ec1a5f973 ("netfilter/ipvs: clear ipvs_property flag when
SKB net namespace changed"). This patch just clears it in spite of
netns.

Fixes: 2b5ec1a5f973 ("netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed")
Signed-off-by: Philo Lu &lt;lulie@linux.alibaba.com&gt;
Acked-by: Julian Anastasov &lt;ja@ssi.bg&gt;
Link: https://patch.msgid.link/20250222033518.126087-1-lulie@linux.alibaba.com
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: core: reject skb_copy(_expand) for fraglist GSO skbs</title>
<updated>2024-05-17T10:02:06+00:00</updated>
<author>
<name>Felix Fietkau</name>
<email>nbd@nbd.name</email>
</author>
<published>2024-04-27T18:24:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=cfe34d86ef9765c388f145039006bb79b6c81ac6'/>
<id>cfe34d86ef9765c388f145039006bb79b6c81ac6</id>
<content type='text'>
[ Upstream commit d091e579b864fa790dd6a0cd537a22c383126681 ]

SKB_GSO_FRAGLIST skbs must not be linearized, otherwise they become
invalid. Return NULL if such an skb is passed to skb_copy or
skb_copy_expand, in order to prevent a crash on a potential later
call to skb_gso_segment.

Fixes: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.")
Signed-off-by: Felix Fietkau &lt;nbd@nbd.name&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit d091e579b864fa790dd6a0cd537a22c383126681 ]

SKB_GSO_FRAGLIST skbs must not be linearized, otherwise they become
invalid. Return NULL if such an skb is passed to skb_copy or
skb_copy_expand, in order to prevent a crash on a potential later
call to skb_gso_segment.

Fixes: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.")
Signed-off-by: Felix Fietkau &lt;nbd@nbd.name&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: mctp: copy skb ext data when fragmenting</title>
<updated>2024-03-26T22:19:34+00:00</updated>
<author>
<name>Jeremy Kerr</name>
<email>jk@codeconstruct.com.au</email>
</author>
<published>2024-02-19T09:51:54+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=be50365391a760853e1eb08ecaa4c3aad099788f'/>
<id>be50365391a760853e1eb08ecaa4c3aad099788f</id>
<content type='text'>
[ Upstream commit 1394c1dec1c619a46867ed32791a29695372bff8 ]

If we're fragmenting on local output, the original packet may contain
ext data for the MCTP flows. We'll want this in the resulting fragment
skbs too.

So, do a skb_ext_copy() in the fragmentation path, and implement the
MCTP-specific parts of an ext copy operation.

Fixes: 67737c457281 ("mctp: Pass flow data &amp; flow release events to drivers")
Reported-by: Jian Zhang &lt;zhangjian.3032@bytedance.com&gt;
Signed-off-by: Jeremy Kerr &lt;jk@codeconstruct.com.au&gt;
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 1394c1dec1c619a46867ed32791a29695372bff8 ]

If we're fragmenting on local output, the original packet may contain
ext data for the MCTP flows. We'll want this in the resulting fragment
skbs too.

So, do a skb_ext_copy() in the fragmentation path, and implement the
MCTP-specific parts of an ext copy operation.

Fixes: 67737c457281 ("mctp: Pass flow data &amp; flow release events to drivers")
Reported-by: Jian Zhang &lt;zhangjian.3032@bytedance.com&gt;
Signed-off-by: Jeremy Kerr &lt;jk@codeconstruct.com.au&gt;
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: prevent mss overflow in skb_segment()</title>
<updated>2024-01-10T16:16:59+00:00</updated>
<author>
<name>Eric Dumazet</name>
<email>edumazet@google.com</email>
</author>
<published>2023-12-12T16:46:21+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=95b3904a261a9f810205da560e802cc326f50d77'/>
<id>95b3904a261a9f810205da560e802cc326f50d77</id>
<content type='text'>
[ Upstream commit 23d05d563b7e7b0314e65c8e882bc27eac2da8e7 ]

Once again syzbot is able to crash the kernel in skb_segment() [1]

GSO_BY_FRAGS is a forbidden value, but unfortunately the following
computation in skb_segment() can reach it quite easily :

	mss = mss * partial_segs;

65535 = 3 * 5 * 17 * 257, so many initial values of mss can lead to
a bad final result.

Make sure to limit segmentation so that the new mss value is smaller
than GSO_BY_FRAGS.

[1]

general protection fault, probably for non-canonical address 0xdffffc000000000e: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
CPU: 1 PID: 5079 Comm: syz-executor993 Not tainted 6.7.0-rc4-syzkaller-00141-g1ae4cd3cbdd0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
RIP: 0010:skb_segment+0x181d/0x3f30 net/core/skbuff.c:4551
Code: 83 e3 02 e9 fb ed ff ff e8 90 68 1c f9 48 8b 84 24 f8 00 00 00 48 8d 78 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 &lt;0f&gt; b6 04 02 84 c0 74 08 3c 03 0f 8e 8a 21 00 00 48 8b 84 24 f8 00
RSP: 0018:ffffc900043473d0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000010046 RCX: ffffffff886b1597
RDX: 000000000000000e RSI: ffffffff886b2520 RDI: 0000000000000070
RBP: ffffc90004347578 R08: 0000000000000005 R09: 000000000000ffff
R10: 000000000000ffff R11: 0000000000000002 R12: ffff888063202ac0
R13: 0000000000010000 R14: 000000000000ffff R15: 0000000000000046
FS: 0000555556e7e380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020010000 CR3: 0000000027ee2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
&lt;TASK&gt;
udp6_ufo_fragment+0xa0e/0xd00 net/ipv6/udp_offload.c:109
ipv6_gso_segment+0x534/0x17e0 net/ipv6/ip6_offload.c:120
skb_mac_gso_segment+0x290/0x610 net/core/gso.c:53
__skb_gso_segment+0x339/0x710 net/core/gso.c:124
skb_gso_segment include/net/gso.h:83 [inline]
validate_xmit_skb+0x36c/0xeb0 net/core/dev.c:3626
__dev_queue_xmit+0x6f3/0x3d60 net/core/dev.c:4338
dev_queue_xmit include/linux/netdevice.h:3134 [inline]
packet_xmit+0x257/0x380 net/packet/af_packet.c:276
packet_snd net/packet/af_packet.c:3087 [inline]
packet_sendmsg+0x24c6/0x5220 net/packet/af_packet.c:3119
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg+0xd5/0x180 net/socket.c:745
__sys_sendto+0x255/0x340 net/socket.c:2190
__do_sys_sendto net/socket.c:2202 [inline]
__se_sys_sendto net/socket.c:2198 [inline]
__x64_sys_sendto+0xe0/0x1b0 net/socket.c:2198
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f8692032aa9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 &lt;48&gt; 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff8d685418 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f8692032aa9
RDX: 0000000000010048 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00000000000f4240 R08: 0000000020000540 R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff8d685480
R13: 0000000000000001 R14: 00007fff8d685480 R15: 0000000000000003
&lt;/TASK&gt;
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:skb_segment+0x181d/0x3f30 net/core/skbuff.c:4551
Code: 83 e3 02 e9 fb ed ff ff e8 90 68 1c f9 48 8b 84 24 f8 00 00 00 48 8d 78 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 &lt;0f&gt; b6 04 02 84 c0 74 08 3c 03 0f 8e 8a 21 00 00 48 8b 84 24 f8 00
RSP: 0018:ffffc900043473d0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000010046 RCX: ffffffff886b1597
RDX: 000000000000000e RSI: ffffffff886b2520 RDI: 0000000000000070
RBP: ffffc90004347578 R08: 0000000000000005 R09: 000000000000ffff
R10: 000000000000ffff R11: 0000000000000002 R12: ffff888063202ac0
R13: 0000000000010000 R14: 000000000000ffff R15: 0000000000000046
FS: 0000555556e7e380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020010000 CR3: 0000000027ee2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Fixes: 3953c46c3ac7 ("sk_buff: allow segmenting based on frag sizes")
Signed-off-by: Eric Dumazet &lt;edumazet@google.com&gt;
Cc: Marcelo Ricardo Leitner &lt;marcelo.leitner@gmail.com&gt;
Reviewed-by: Willem de Bruijn &lt;willemb@google.com&gt;
Link: https://lore.kernel.org/r/20231212164621.4131800-1-edumazet@google.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
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[ Upstream commit 23d05d563b7e7b0314e65c8e882bc27eac2da8e7 ]

Once again syzbot is able to crash the kernel in skb_segment() [1]

GSO_BY_FRAGS is a forbidden value, but unfortunately the following
computation in skb_segment() can reach it quite easily :

	mss = mss * partial_segs;

65535 = 3 * 5 * 17 * 257, so many initial values of mss can lead to
a bad final result.

Make sure to limit segmentation so that the new mss value is smaller
than GSO_BY_FRAGS.

[1]

general protection fault, probably for non-canonical address 0xdffffc000000000e: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
CPU: 1 PID: 5079 Comm: syz-executor993 Not tainted 6.7.0-rc4-syzkaller-00141-g1ae4cd3cbdd0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
RIP: 0010:skb_segment+0x181d/0x3f30 net/core/skbuff.c:4551
Code: 83 e3 02 e9 fb ed ff ff e8 90 68 1c f9 48 8b 84 24 f8 00 00 00 48 8d 78 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 &lt;0f&gt; b6 04 02 84 c0 74 08 3c 03 0f 8e 8a 21 00 00 48 8b 84 24 f8 00
RSP: 0018:ffffc900043473d0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000010046 RCX: ffffffff886b1597
RDX: 000000000000000e RSI: ffffffff886b2520 RDI: 0000000000000070
RBP: ffffc90004347578 R08: 0000000000000005 R09: 000000000000ffff
R10: 000000000000ffff R11: 0000000000000002 R12: ffff888063202ac0
R13: 0000000000010000 R14: 000000000000ffff R15: 0000000000000046
FS: 0000555556e7e380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020010000 CR3: 0000000027ee2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
&lt;TASK&gt;
udp6_ufo_fragment+0xa0e/0xd00 net/ipv6/udp_offload.c:109
ipv6_gso_segment+0x534/0x17e0 net/ipv6/ip6_offload.c:120
skb_mac_gso_segment+0x290/0x610 net/core/gso.c:53
__skb_gso_segment+0x339/0x710 net/core/gso.c:124
skb_gso_segment include/net/gso.h:83 [inline]
validate_xmit_skb+0x36c/0xeb0 net/core/dev.c:3626
__dev_queue_xmit+0x6f3/0x3d60 net/core/dev.c:4338
dev_queue_xmit include/linux/netdevice.h:3134 [inline]
packet_xmit+0x257/0x380 net/packet/af_packet.c:276
packet_snd net/packet/af_packet.c:3087 [inline]
packet_sendmsg+0x24c6/0x5220 net/packet/af_packet.c:3119
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg+0xd5/0x180 net/socket.c:745
__sys_sendto+0x255/0x340 net/socket.c:2190
__do_sys_sendto net/socket.c:2202 [inline]
__se_sys_sendto net/socket.c:2198 [inline]
__x64_sys_sendto+0xe0/0x1b0 net/socket.c:2198
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f8692032aa9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 &lt;48&gt; 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff8d685418 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f8692032aa9
RDX: 0000000000010048 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00000000000f4240 R08: 0000000020000540 R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff8d685480
R13: 0000000000000001 R14: 00007fff8d685480 R15: 0000000000000003
&lt;/TASK&gt;
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:skb_segment+0x181d/0x3f30 net/core/skbuff.c:4551
Code: 83 e3 02 e9 fb ed ff ff e8 90 68 1c f9 48 8b 84 24 f8 00 00 00 48 8d 78 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 &lt;0f&gt; b6 04 02 84 c0 74 08 3c 03 0f 8e 8a 21 00 00 48 8b 84 24 f8 00
RSP: 0018:ffffc900043473d0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000010046 RCX: ffffffff886b1597
RDX: 000000000000000e RSI: ffffffff886b2520 RDI: 0000000000000070
RBP: ffffc90004347578 R08: 0000000000000005 R09: 000000000000ffff
R10: 000000000000ffff R11: 0000000000000002 R12: ffff888063202ac0
R13: 0000000000010000 R14: 000000000000ffff R15: 0000000000000046
FS: 0000555556e7e380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020010000 CR3: 0000000027ee2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Fixes: 3953c46c3ac7 ("sk_buff: allow segmenting based on frag sizes")
Signed-off-by: Eric Dumazet &lt;edumazet@google.com&gt;
Cc: Marcelo Ricardo Leitner &lt;marcelo.leitner@gmail.com&gt;
Reviewed-by: Willem de Bruijn &lt;willemb@google.com&gt;
Link: https://lore.kernel.org/r/20231212164621.4131800-1-edumazet@google.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
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