linux.git/net/core, branch v7.3-rc2

net: Remove conflicting altnames for dying netns in __dev_change_net_namespace().

2026-09-03T01:30:00+00:00

syzbot reported the warning in cfg80211_pernet_exit(). [0]

The repro does the following:

  1. create two device in root netns and non-root netns
  2. assign the same altname for the two devices
  3. remove the non-root netns

Since commit 7663d522099e ("net: check for altname conflicts
when changing netdev's netns"), cfg80211_switch_netns() and
cfg802154_switch_netns() fail if init_net has a device with the
conflicting altname.

default_device_exit_net() had the same issue and commit d09486a04f5d
("net: fix removing a namespace with conflicting altnames") fixed it.

cfg80211_pernet_exit() and cfg802154_pernet_exit() need the same fix.

Let's generalise the fix by removing conflicting altnames for dying
netns in __dev_change_net_namespace().

[0]:
cfg80211_switch_netns(rdev, &init_net)
WARNING: net/wireless/core.c:1871 at cfg80211_pernet_exit+0xd5/0x120 net/wireless/core.c:1871, CPU#1: kworker/u8:9/1160
Modules linked in:
CPU: 1 UID: 0 PID: 1160 Comm: kworker/u8:9 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: netns cleanup_net
RIP: 0010:cfg80211_pernet_exit+0xd5/0x120 net/wireless/core.c:1871
Code: e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 b4 ef 0e f7 4d 8b 36 49 81 fe 20 10 4a 90 74 12 e8 03 3d 9f f6 eb 85 e8 fc 3c 9f f6 90 <0f> 0b 90 eb cc e8 f1 3c 9f f6 eb 05 e8 ea 3c 9f f6 5b 41 5c 41 5e
RSP: 0018:ffffc900057a78f0 EFLAGS: 00010293
RAX: ffffffff8b287154 RBX: ffff88807ba72780 RCX: ffff8880213e8000
RDX: 0000000000000000 RSI: 00000000ffffffef RDI: 0000000000000000
RBP: 00000000ffffffef R08: ffffffff9024cc67 R09: 0000000000000000
R10: fffff52000af4eb0 R11: fffffbfff204998d R12: dffffc0000000000
R13: ffffffff904a1080 R14: ffff888144ed0008 R15: ffff888144ed0e20
FS:  0000000000000000(0000) GS:ffff888124de6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005642de0a8a70 CR3: 000000007a40c000 CR4: 00000000003526f0
Call Trace:
 
 ops_exit_list net/core/net_namespace.c:200 [inline]
 ops_undo_list+0x43d/0x8d0 net/core/net_namespace.c:253
 cleanup_net+0x572/0x810 net/core/net_namespace.c:706
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 

Fixes: 36fbf1e52bd3 ("net: rtnetlink: add linkprop commands to add and delete alternative ifnames")
Reported-by: syzbot+74f338e09f1ef3ee6457@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/6a96219e.04428c52.29b18.0001.GAE@google.com/T/
Signed-off-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20260901005550.2042357-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski

net: psp: do not inherit the Rx association on clone

2026-09-01T13:12:24+00:00

sk->psp_assoc sits past sk_dontcopy_end, so sock_copy() copies it into
every socket accepted from a listener without taking a reference, while
inet_sock_destruct() puts for every inet socket. psp_twsk_init() does
refcount_inc() for the timewait socket, so a child closing through
TIME_WAIT cancels its own put and leaves the association with one
reference and N timewait sockets holding the same pointer. Closing the
listener frees it, and the timewait timers then put freed memory.

Rejecting the association on a listening socket is not sufficient: a socket
can acquire one while established and then be turned back into a listener,
because tcp_disconnect() leaves sk->psp_assoc in place.

  BUG: KASAN: slab-use-after-free in psp_twsk_assoc_free+0x6f/0xf0
  Write of size 4 at addr ffff888110f9255c by task swapper/7/0
   psp_twsk_assoc_free+0x6f/0xf0
   inet_twsk_put+0xda/0x1b0
   call_timer_fn+0x53/0x2e0
   __run_timers+0x764/0xa80
  Freed by task 99:
   kfree+0x1a7/0x500
   process_one_work+0x7ec/0x1100

An association carries a per-connection SPI and key, so a child must not
inherit the parent's. Clear it on clone.

Fixes: 6b46ca260e22 ("net: psp: add socket security association code")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Norbert Szetei 
Reviewed-by: Daniel Zahka 
Link: https://patch.msgid.link/BC10EB92-ABB3-41B2-AB16-266BEEBE18C0@doyensec.com
Signed-off-by: Paolo Abeni

page_pool: keep frag_offset aligned for odd-sized requests

2026-08-31T23:24:51+00:00

page_pool_alloc_frag_netmem() rounds the requested fragment size with

	size = ALIGN(size, dma_get_cache_alignment());

dma_get_cache_alignment() returns 1 unless the architecture defines
ARCH_DMA_MINALIGN, which DMA-coherent architectures such as x86 do not.
There the ALIGN() is a no-op and pool->frag_offset advances by the raw,
unrounded size.

A single caller asking for an odd size then leaves frag_offset misaligned
for every fragment carved out of that page afterwards.  The pool is shared,
so the damage is not confined to the caller that caused it.

The per-cpu system_page_pool used by generic XDP hits this.
skb_pp_cow_data() allocates its fragments with the raw packet length:

	size = min_t(u32, len, PAGE_SIZE);
	truesize = size;
	page = page_pool_dev_alloc(pool, &page_off, &truesize);

leaving frag_offset odd for whatever is carved out of that page next.  Its
own head allocation is already aligned -- SKB_HEAD_ALIGN(size) plus the
XDP_PACKET_HEADROOM its callers pass -- so it is a later user of the shared
pool that pays: page_pool_dev_alloc_va() returns a misaligned buffer,
napi_build_skb() installs it as skb->head, and skb_shinfo(skb) ==
skb->head + skb->end is misaligned with it.

skb_shinfo()->dataref is a 4-byte atomic_t at offset 0x20, so the
atomic_inc() in __skb_clone() straddles a cache line.  On x86 with split
lock detection -- fatal for kernel split locks by default -- this panics
the machine:

  Oops: Split lock detected
  RIP: 0010:skb_clone+0x154/0x1e0
  Call Trace:
   
   raw_local_deliver+0x1ed/0x2c0
   ip_protocol_deliver_rcu+0x54/0x1c0
   ip_local_deliver_finish+0x85/0x100
   ip_local_deliver+0x67/0x100
   __netif_receive_skb_one_core+0x85/0xa0
   process_backlog+0x87/0x130

Reproduced by attaching any generic-mode XDP program to loopback and
opening a RAW IPPROTO_UDP socket, which makes raw_local_deliver() clone
every locally delivered UDP packet; ordinary DNS traffic then triggers it,
roughly once per 2500 clones.  Observed on 6.12.101 and 7.1.8.

Tracing page_pool_alloc_frag_netmem() over one such run shows the
amplification -- two odd-sized requests, nine misaligned offsets:

  requested size & 7:   0: 17035    5: 1    7: 1
  frag_offset & 7:      0: 17028    3: 1    4: 1    5: 1    6: 1    7: 5

and skb_pp_cow_data() returning heads that were aligned on entry:

  head 0xffff8f4c86aeac00 -> 0xffff8f4c53a9a9c4 (&7=4)
  head 0xffff8f4d6a8a42c0 -> 0xffff8f4c4f7b7a45 (&7=5)

Round the fragment size up to at least the alignment struct skb_shared_info
requires, so fragments are always suitably aligned for the objects callers
build on them.  Architectures needing a larger DMA alignment keep it.

This also makes the remainder computed in page_pool_alloc_netmem(),

	*size = max_size - *offset;

aligned, since max_size is a power of two -- which fixes the matching
misalignment of skb->end.

Verified with a controlled A/B under QEMU/KVM: same tree, same config,
same compiler, same rootfs and identical traffic, differing only by this
patch.  A SEC("xdp.frags") XDP_PASS program on lo plus UDP datagrams
larger than max_head_size drives skb_pp_cow_data()'s fragment loop, which
passes raw packet lengths to the pool.  Measured at the return of
skb_pp_cow_data():

                          unpatched   patched
  skb_pp_cow_data calls       40800     40800
  misaligned skb->head         1120         0
  dataref at line offset >60     80         0

The last row counts the accesses that actually fault:
skb_shinfo()->dataref sits at head+end+0x20 and is a 4-byte atomic, so
`lock incl` splits a 64-byte cache line only when that address lands at
offset 61..63.  All 80 occurrences were at offset 61; the panic reported
above was at offset 62.  Eliminating the misalignment removes every one
of them.

Same class of bug as commit 3bed3cc4156e ("net: Do not allocate page
fragments that are not skb aligned"), which fixed the older
netdev_alloc_frag()/napi_alloc_frag() allocators.

Fixes: 53e0961da1c7 ("page_pool: add frag page recycling support in page pool")
Cc: stable@vger.kernel.org
Signed-off-by: Florian Schauer 
Acked-by: Jesper Dangaard Brouer 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/20260828060822.2628276-1-florian@schauer.to
Signed-off-by: Jakub Kicinski

net: iptunnel: fix stale transport header during tunnel decapsulation

2026-08-28T22:53:46+00:00

Syzbot reported a crash in qdisc_pkt_len_segs_init() caused by a stale
transport_header offset after tunnel decapsulation.

BUG: unable to handle page fault for address: ffffed102091a42e
Oops: Oops: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 340 Comm: qdisc_uaf_repro Not tainted 7.2.0-rc4-00061-g248951ddc14d #256 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__asan_load2

qdisc_pkt_len_segs_init (net/core/dev.c:4145)
__dev_queue_xmit (net/core/dev.c:4787)
br_dev_queue_push_xmit (net/bridge/br_forward.c:53)
br_handle_frame_finish (net/bridge/br_input.c:229)
br_handle_frame (net/bridge/br_input.c:315)
__netif_receive_skb_core.constprop.0 (net/core/dev.c:6099)
__netif_receive_skb_list_core (net/core/dev.c:6287)
netif_receive_skb_list_internal (net/core/dev.c:6445)
napi_complete_done (net/core/dev.c:6813)
gro_cell_poll (net/core/gro_cells.c:74)
__napi_poll (net/core/dev.c:7735)
net_rx_action (net/core/dev.c:7798 net/core/dev.c:7955)
handle_softirqs (kernel/softirq.c:622)
do_softirq (kernel/softirq.c:523  kernel/softirq.c:510 )
__local_bh_enable_ip (kernel/softirq.c:450)
tun_get_user (drivers/net/tun.c:1986 (discriminator 1))
tun_chr_write_iter (drivers/net/tun.c:2032)

The issue is completely latent until qdisc read transport header in
commit 7fb4c1967011 ("net: pull headers in qdisc_pkt_len_segs_init()").
The crash requires four conditions to line up:

1. The incoming packet is encapsulated and carries GSO metadata. The outer
   transport header offset is stored in skb->transport_header while the
   packet is still in the outer tunnel context.
2. The tunnel receiver strips the outer headers. skb->data is advanced to
   the inner frame, but skb->transport_header is left pointing to the
   now-removed outer L4 header, so it becomes a negative offset relative to
   the new data.
3. The inner frame is not delivered to the local IP stack. Instead, it
   is forwarded at L2 by a bridge or HSR, so ip_rcv_core() never runs and
   the transport header is not reset to the inner L4 offset.
4. The forwarding path calls __dev_queue_xmit(), which enters
   qdisc_pkt_len_segs_init(). That function computes the GSO header length
   from skb_transport_offset(skb). Because the offset is negative, the
   unsigned cast overflows and pskb_may_pull(skb, hdr_len +
   sizeof(struct tcphdr)) reads past the end of the skb, triggering a
   KASAN fault or page fault.

The issue specifically requires GSO packets (shinfo->gso_size != 0), which
are processed/aggregated through gro_cells. Fix this by clearing
transport_header to the ~0U sentinel in gro_cell for all tunnnel driver.
GTP does not support GRO/GSO, drop the evil GSO packets in GTP directly.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+83181a31faf9455499c5@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69de2bee.a00a0220.475f0.0041.GAE@google.com/T/
Suggested-by: Eric Dumazet 
Signed-off-by: Dong Chenchen 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/20260825123909.1463121-1-dongchenchen2@huawei.com
Signed-off-by: Jakub Kicinski

net: Guard for gso_segs overflow in skb_segment

2026-08-27T13:47:18+00:00

skb_segment calculates 32-bit partial_segs as len / gso_size, and then
assigns it to the 16-bit gso_segs field. The division might overflow in
some edge cases where the SKB is BIG TCP (65536 <= len <= 8*65535), and
gso_size < TCP_MIN_GSO_SIZE = 8. While normally this can't happen due to
TCP_MIN_GSO_SIZE, an AF_PACKET PACKET_VNET_HDR socket could generate
such a malformed packet until the previous patch.

Blocking malformed virtio_net packets was implemented in the previous
patch, but this patch clamps partial_segs in skb_segment itself for more
generic robustness. Should len / gso_size happen to be bigger than
65535 in partial GSO, skb_segment will now just produce more than two
output SKBs, all of which will be valid with gso_segs <= 65535.

In order to catch possible other cases of too many partial_segs, add a
DEBUG_NET_WARN_ON_ONCE when len / gso_size happens to be too big.

Signed-off-by: Alice Mikityanska 
Link: https://patch.msgid.link/20260822120117.1163423-3-alice.kernel@fastmail.im
Signed-off-by: Paolo Abeni

net: fix a resource leak in copy_net_ns() error handling path

2026-08-25T10:30:55+00:00

Currently, preinit_net() does two things:

  (1) call ns_common_init() which might fail
  (2) initialize resources which does not fail

However, preinit_net() is returning early when (1) fails, and copy_net_ns()
is jumping to the dec_ucounts: label. As a result, resources allocated by
net_alloc() are leaking. We need to call key_remove_domain() and
net_passive_dec() in order to release resources allocated by net_alloc().

We cannot simply jump to the put_userns: label when preinit_net() failed,
for (2) is not yet done. But we can reorder (1) and (2), for there is no
dependency between (1) and (2). Therefore, this patch decouples (1) from
preinit_net() and changes preinit_net() back to a void function, and calls
ns_common_init() after preinit_net() succeeded. Then, we can jump to
immediately after ns_common_free() of the put_userns: label.

Reported-by: sashiko (no mail address)
Closes: https://sashiko.dev/#/patchset/af7dabf3-d0d7-46dc-a878-e1715b3c9ac6%40I-love.SAKURA.ne.jp
Fixes: 08027f6b790b ("net: use ns_common_init()")
Signed-off-by: Tetsuo Handa 
Link: https://patch.msgid.link/c182cf90-1ed7-435b-88f7-9f00e88a0487@I-love.SAKURA.ne.jp
Signed-off-by: Paolo Abeni

net: core: fix head-page leak in skb_zerocopy

2026-08-25T09:28:44+00:00

When skb_orphan_frags() throws -ENOMEM, skb_copy_ubufs() may have
already reallocated and replaced 'from->head'. Accessing from->head to
drop the old refcount leaks the original head page, and erroneously
puts an unrelated new buffer. Use the local 'page' tracker variable
instead to drop the reference properly.

Fixes: 36d5fe6a0007 ("core, nfqueue, openvswitch: Orphan frags in skb_zerocopy and handle errors")
Signed-off-by: Mina Almasry 
Link: https://patch.msgid.link/20260823183602.1051453-2-almasrymina@google.com
Signed-off-by: Paolo Abeni

net: core: check skb_frags_readable before uncloning in skb_copy_ubufs

2026-08-25T09:28:40+00:00

skb_copy_ubufs drops clones and modifies the SKB via pskb_expand_head()
before checking for !skb_frags_readable(skb). This alters the SKB
geometry prior to throwing an -EFAULT on an invalid SKB. Check
readability first.

Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags")
Signed-off-by: Mina Almasry 
Link: https://patch.msgid.link/20260823183602.1051453-1-almasrymina@google.com
Signed-off-by: Paolo Abeni

net: skbuff: don't touch shared zerocopy state in skb_tx_error()

2026-08-25T07:36:47+00:00

skb_tx_error() completes the zerocopy uarg and clears
SKBFL_ALL_ZEROCOPY, and skb_zcopy_downgrade_managed() clears
SKBFL_MANAGED_FRAG_REFS. Both live in skb_shinfo(), which every clone
shares, while the caller only owns the reference it is about to drop.
Through a clone it tells the producer its pages are free and drops
SKBFL_SHARED_FRAG for an skb that is still in flight.

Open vSwitch reaches this with a non-last OVS_ACTION_ATTR_RECIRC:
clone_execute() sends a skb_clone() into ovs_dp_process_packet() while
do_execute_actions() keeps forwarding the original, and skb_clone()
does not privatise the frags here -- skb_orphan_frags() returns early
on SKBFL_DONT_ORPHAN. A flow miss on the clone then strips the marker
from the packet still being forwarded, and a later local ESP delivery
decrypts in place over frags it does not own privately.

Skip it for a cloned skb. Nothing is lost: skb_release_data() clears
the zerocopy state once the last reference to the shared data goes.

Fixes: 25121173f7b1 ("skb: api to report errors for zero copy skbs")
Cc: stable@vger.kernel.org
Suggested-by: Ilya Maximets 
Signed-off-by: Norbert Szetei 
Reviewed-by: Ilya Maximets 
Tested-by: Jongmin Jang 
Reviewed-by: Willem de Bruijn 
Link: https://patch.msgid.link/CFAB292A-674B-4C14-BB2C-BB8830AD5659@doyensec.com
Signed-off-by: Paolo Abeni

net: skbuff: don't skb_tx_error() the source skb in skb_zerocopy()

2026-08-25T07:36:47+00:00

skb_zerocopy() copies frags from @from into @to. On an
skb_orphan_frags() failure it calls skb_tx_error(@from), a destructive
operation on the source skb the copy helper does not own. That completes
@from's zerocopy uarg and clears SKBFL_ALL_ZEROCOPY, including the
SKBFL_SHARED_FRAG page-ownership marker.

Both callers already report the failure on their own drop path.
nfnetlink_queue does it at nla_put_failure, and Open vSwitch does it in
the flow-miss drop arm of ovs_dp_process_packet(), so nothing is lost by
dropping it here.

On Open vSwitch's OVS_ACTION_ATTR_USERSPACE path the skb is not freed on
this error: do_execute_actions() ignores output_userspace()'s return
value and, unless the upcall was the last action, keeps forwarding the
same skb through the flow's remaining actions. The uarg is completed
while that skb is still in flight, telling the producer its buffers are
free, and SKBFL_SHARED_FRAG is cleared on an skb the rest of the stack
still handles. That flag is what makes esp_input() call skb_cow_data()
instead of decrypting in place, so a later local ESP delivery can
decrypt over frags the skb does not own privately.

Leave error reporting to the callers.

Fixes: 36d5fe6a0007 ("core, nfqueue, openvswitch: Orphan frags in skb_zerocopy and handle errors")
Cc: stable@vger.kernel.org
Suggested-by: Ilya Maximets 
Signed-off-by: Norbert Szetei 
Reviewed-by: Ilya Maximets 
Reviewed-by: Willem de Bruijn 
Link: https://patch.msgid.link/6E3A780D-FB87-421F-9964-B1D457D7D106@doyensec.com
Signed-off-by: Paolo Abeni