linux-stable.git/net/ipv6, branch v7.2.6 Linux kernel stable tree Revert "esp: do not unref managed frag pages in esp_ssg_unref()" 2026-09-14T11:41:11+00:00 Steffen Klassert steffen.klassert@secunet.com 2026-08-17T05:17:58+00:00 2bfcedbf68cbd311f2ea7ed2fec55121a91f48cf [ Upstream commit 0fda52de8bbd4ca9a852c8a7ef6536cf82bd71fd ] This reverts commit 21697720ff43b8dfa25b8e8d9ca7f56f4597fc80. The patch does not fix the issue completely, so revert for now and wait for an updated version. Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 0fda52de8bbd4ca9a852c8a7ef6536cf82bd71fd ]

This reverts commit 21697720ff43b8dfa25b8e8d9ca7f56f4597fc80.

The patch does not fix the issue completely, so revert for
now and wait for an updated version.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
ip6mr: do not clone dst in ip6mr_cache_report() 2026-09-14T11:41:01+00:00 Eric Dumazet edumazet@google.com 2026-08-18T17:27:55+00:00 4a674afaae4136c71943aa3e35d433676fd40e8f [ Upstream commit 235b42b5860189eb8c27c36435ad932cae65a734 ] IPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU. When an ingress multicast packet misses MFC lookup, ip6mr_cache_unresolved() places the skb onto the unresolved queue, escaping the receive-side RCU grace period. If the underlying route is deleted and freed, and the MFC queue is later resolved with a wrong parent interface, ip6_mr_forward() invokes ip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes dst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab use-after-free. Report packets queued to mroute6_sk (a raw socket) and netlink notifications do not require an attached dst entry. Fix this by: 1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs do not hold a dst. 2. Dropping skb_dst before queuing unresolved skbs in ip6mr_cache_unresolved(), matching the fact that multicast forwarding resolves outgoing routes anew via ip6_route_output(). Fixes: 67f415dd2906 ("ipv6: convert rx data path to not take refcnt on dst") Reported-by: Zero Day Initiative <zdi-disclosures@trendmicro.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn> Link: https://patch.msgid.link/20260818172755.4083692-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 235b42b5860189eb8c27c36435ad932cae65a734 ]

IPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU.
When an ingress multicast packet misses MFC lookup,
ip6mr_cache_unresolved() places the skb onto the unresolved queue,
escaping the receive-side RCU grace period.

If the underlying route is deleted and freed, and the MFC queue is later
resolved with a wrong parent interface, ip6_mr_forward() invokes
ip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes
dst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab
use-after-free.

Report packets queued to mroute6_sk (a raw socket) and netlink
notifications do not require an attached dst entry.

Fix this by:
1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs
   do not hold a dst.
2. Dropping skb_dst before queuing unresolved skbs in
   ip6mr_cache_unresolved(), matching the fact that multicast
   forwarding resolves outgoing routes anew via ip6_route_output().

Fixes: 67f415dd2906 ("ipv6: convert rx data path to not take refcnt on dst")
Reported-by: Zero Day Initiative <zdi-disclosures@trendmicro.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
Link: https://patch.msgid.link/20260818172755.4083692-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
ipv6: avoid divide by zero in rt6_multipath_rebalance 2026-09-14T11:41:01+00:00 Cen Zhang (Microsoft) blbllhy@gmail.com 2026-08-17T01:32:37+00:00 f82b5dbb2fef65b52a62d5ffe05e0483c4385a83 [ Upstream commit d2c26c2911dd1a363c488add4fb63eb5f0f28f87 ] rt6_multipath_rebalance() calculates the total eligible nexthop weight in one pass and programs upper bounds in a second pass. Since RTM_NEWROUTE is RTNL-free, a concurrent ignore_routes_with_linkdown update can make the first pass return zero while the second sees an eligible nexthop, causing rt6_upper_bound_set() to divide by zero. UBSAN: division-overflow in net/ipv6/route.c:4845:17 Oops: divide error: 0000 [#1] SMP KASAN NOPTI rt6_upper_bound_set() net/ipv6/route.c:4845 rt6_multipath_rebalance() fib6_add_rt2node() ip6_route_multipath_add() inet6_rtm_newroute() Skip upper-bound calculation when the first pass reports a zero total. This respects the lock-free performance considerations here and solves insecure scenarios. Fixes: bd11ff421d36 ("ipv6: Get rid of RTNL for SIOCDELRT and RTM_DELROUTE.") Reported-by: AutonomousCodeSecurity@microsoft.com Reported-by: Xiang Mei (Microsoft) <xmei5@asu.edu> Reported-by: Cen Zhang (Microsoft) <blbllhy@gmail.com> Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Link: https://patch.msgid.link/20260817013237.2797-1-blbllhy@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit d2c26c2911dd1a363c488add4fb63eb5f0f28f87 ]

rt6_multipath_rebalance() calculates the total eligible nexthop weight
in one pass and programs upper bounds in a second pass. Since
RTM_NEWROUTE is RTNL-free, a concurrent
ignore_routes_with_linkdown update can make the first pass return zero
while the second sees an eligible nexthop, causing
rt6_upper_bound_set() to divide by zero.

UBSAN: division-overflow in net/ipv6/route.c:4845:17
Oops: divide error: 0000 [#1] SMP KASAN NOPTI
  rt6_upper_bound_set() net/ipv6/route.c:4845
  rt6_multipath_rebalance()
  fib6_add_rt2node()
  ip6_route_multipath_add()
  inet6_rtm_newroute()

Skip upper-bound calculation when the first pass reports a zero total.
This respects the lock-free performance considerations here and solves
insecure scenarios.

Fixes: bd11ff421d36 ("ipv6: Get rid of RTNL for SIOCDELRT and RTM_DELROUTE.")
Reported-by: AutonomousCodeSecurity@microsoft.com
Reported-by: Xiang Mei (Microsoft) <xmei5@asu.edu>
Reported-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260817013237.2797-1-blbllhy@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
esp: do not unref managed frag pages in esp_ssg_unref() 2026-09-14T11:39:26+00:00 Maher Azzouzi maherazz04@gmail.com 2026-07-12T17:05:30+00:00 26b6b14c7a0368e317a1e9fb5144ebe6f8d495cf [ Upstream commit 21697720ff43b8dfa25b8e8d9ca7f56f4597fc80 ] esp_ssg_unref() releases the page references held on the source scatterlist after the AEAD operation completes. It calls skb_page_unref() on every frag page for an out-of-place transform (req->src != req->dst), and in the error path of esp_output_tail() (already_unref == true) on the request's own scatterlist. This is wrong when the skb carries managed frags (SKBFL_MANAGED_FRAG_REFS). Managed frags are owned by a zerocopy ubuf and the skb does not hold a per-frag page reference; io_uring SEND_ZC with a registered buffer attaches the bvec pages this way via io_sg_from_iter(). The rest of the stack honours this invariant: skb_release_data() skips the per-frag unref when SKBFL_MANAGED_FRAG_REFS is set, and skb_zcopy_managed() is the guard used at the other unref sites. esp_ssg_unref() is missing that guard, so for a managed-frag skb it drops a page reference the skb never acquired. This can underflow the page reference count and free a page that is still in use. Guard the function with skb_zcopy_managed() so both unref paths are skipped for managed-frag skbs, matching skb_release_data(). Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible") Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible") Signed-off-by: Maher Azzouzi <maherazz04@gmail.com> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 21697720ff43b8dfa25b8e8d9ca7f56f4597fc80 ]

esp_ssg_unref() releases the page references held on the source
scatterlist after the AEAD operation completes.  It calls
skb_page_unref() on every frag page for an out-of-place transform
(req->src != req->dst), and in the error path of esp_output_tail()
(already_unref == true) on the request's own scatterlist.

This is wrong when the skb carries managed frags
(SKBFL_MANAGED_FRAG_REFS).  Managed frags are owned by a zerocopy ubuf
and the skb does not hold a per-frag page reference; io_uring SEND_ZC
with a registered buffer attaches the bvec pages this way via
io_sg_from_iter().  The rest of the stack honours this invariant:
skb_release_data() skips the per-frag unref when SKBFL_MANAGED_FRAG_REFS
is set, and skb_zcopy_managed() is the guard used at the other unref
sites.

esp_ssg_unref() is missing that guard, so for a managed-frag skb it
drops a page reference the skb never acquired.  This can underflow the
page reference count and free a page that is still in use.

Guard the function with skb_zcopy_managed() so both unref paths are
skipped for managed-frag skbs, matching skb_release_data().

Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
Signed-off-by: Maher Azzouzi <maherazz04@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full 2026-09-14T11:39:26+00:00 Xiang Mei xmei5@asu.edu 2026-07-04T21:03:32+00:00 5f35a29a5eed3d80befd32050843ac88dea3d61a [ Upstream commit 5d9e3bf34fec9a5d237e4b7cef4a707bc2e091bc ] The depth check in xfrm6_input_addr() is off by one: if (1 + sp->len == XFRM_MAX_DEPTH) goto drop; ... sp->xvec[sp->len++] = x; xfrm_input() can leave sp->len == XFRM_MAX_DEPTH, and the transport-mode receive path re-enters IPv6 input via xfrm_trans_reinject() with that secpath preserved. If the inner packet carries a destination-options HAO option or a type-2 routing header, xfrm6_input_addr() is called with sp->len == XFRM_MAX_DEPTH; the check (1 + 6 == 6) is false, so sp->xvec[sp->len++] writes one slot past the 6-element xvec[]. The write stays within the sec_path allocation (invisible to KASAN); UBSAN_BOUNDS flags it and panics under panic_on_warn. Use "sp->len >= XFRM_MAX_DEPTH", matching xfrm_input(). This also restores one chain level the old check rejected at sp->len == 5. UBSAN: array-index-out-of-bounds in net/ipv6/xfrm6_input.c:309:10 index 6 is out of range for type 'xfrm_state *[6]' Fixes: 9473e1f631de ("[XFRM] MIPv6: Fix to input RO state correctly.") Reported-by: Weiming Shi <bestswngs@gmail.com> Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei <xmei5@asu.edu> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 5d9e3bf34fec9a5d237e4b7cef4a707bc2e091bc ]

The depth check in xfrm6_input_addr() is off by one:

  if (1 + sp->len == XFRM_MAX_DEPTH)
          goto drop;
  ...
  sp->xvec[sp->len++] = x;

xfrm_input() can leave sp->len == XFRM_MAX_DEPTH, and the transport-mode
receive path re-enters IPv6 input via xfrm_trans_reinject() with that
secpath preserved. If the inner packet carries a destination-options HAO
option or a type-2 routing header, xfrm6_input_addr() is called with
sp->len == XFRM_MAX_DEPTH; the check (1 + 6 == 6) is false, so
sp->xvec[sp->len++] writes one slot past the 6-element xvec[]. The write
stays within the sec_path allocation (invisible to KASAN); UBSAN_BOUNDS
flags it and panics under panic_on_warn.

Use "sp->len >= XFRM_MAX_DEPTH", matching xfrm_input(). This also
restores one chain level the old check rejected at sp->len == 5.

  UBSAN: array-index-out-of-bounds in net/ipv6/xfrm6_input.c:309:10
  index 6 is out of range for type 'xfrm_state *[6]'

Fixes: 9473e1f631de ("[XFRM] MIPv6: Fix to input RO state correctly.")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
seg6: reset IP6CB after IPv6 decapsulation 2026-09-07T15:37:21+00:00 Zhiling Zou zhilinz@nebusec.ai 2026-08-22T08:49:27+00:00 c73fb911e02b9a766c950bc9707f3e3a96ffd702 commit f967455fb2a5a2079b9eb5823e9ccf359174bf9f upstream. decap_and_validate() pulls the outer SRv6 headers and makes the inner packet the skb network header. The IPv6 control block still contains values collected while parsing the outer packet, including nhoff and extension-header flags. End.DX6 and End.DT6 route the inner IPv6 packet directly to the IPv6 input path. An unprivileged user can reach End.DT6 from a user and net namespace by installing a local SID and injecting an outer packet with Hop-by-Hop and Destination Options headers followed by an SRH and a minimal inner IPv6 packet. The outer extension headers leave a large nhoff in IP6CB. After decapsulation, ip6_protocol_deliver_rcu() uses that stale offset on the inner packet and reads beyond the skb head. KASAN reports: BUG: KASAN: slab-out-of-bounds in ip6_protocol_deliver_rcu ip6_protocol_deliver_rcu+0x1118/0x1450 ip6_input_finish+0x11b/0x240 seg6_local_input_core+0xed/0x2e0 lwtunnel_input+0x1e9/0x4e0 ipv6_rthdr_rcv+0x525f/0x6c50 ip6_protocol_deliver_rcu+0xcb7/0x1450 Before clearing IP6CB for an inner IPv6 packet, save its incoming interface index and L3 slave state. Restore both after the clear and set nhoff to the inner IPv6 base-header nexthdr field. Use IP6CB(skb)->iif rather than skb->skb_iif because VRF processing can replace skb_iif with the L3 master while IP6CB keeps the receiving interface. Preserve IP6SKB_L3SLAVE for the same reason. Fixes: d7a669dd2f8b ("ipv6: sr: add helper functions for seg6local") Cc: stable@vger.kernel.org Reported-by: Vega <vega@nebusec.ai> Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai> Reviewed-by: Andrea Mayer <andrea.mayer@uniroma2.it> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit f967455fb2a5a2079b9eb5823e9ccf359174bf9f upstream.

decap_and_validate() pulls the outer SRv6 headers and makes the inner
packet the skb network header. The IPv6 control block still contains
values collected while parsing the outer packet, including nhoff and
extension-header flags.

End.DX6 and End.DT6 route the inner IPv6 packet directly to the IPv6
input path. An unprivileged user can reach End.DT6 from a user and net
namespace by installing a local SID and injecting an outer packet with
Hop-by-Hop and Destination Options headers followed by an SRH and a
minimal inner IPv6 packet.

The outer extension headers leave a large nhoff in IP6CB. After
decapsulation, ip6_protocol_deliver_rcu() uses that stale offset on the
inner packet and reads beyond the skb head. KASAN reports:

  BUG: KASAN: slab-out-of-bounds in ip6_protocol_deliver_rcu
  ip6_protocol_deliver_rcu+0x1118/0x1450
  ip6_input_finish+0x11b/0x240
  seg6_local_input_core+0xed/0x2e0
  lwtunnel_input+0x1e9/0x4e0
  ipv6_rthdr_rcv+0x525f/0x6c50
  ip6_protocol_deliver_rcu+0xcb7/0x1450

Before clearing IP6CB for an inner IPv6 packet, save its incoming
interface index and L3 slave state. Restore both after the clear and set
nhoff to the inner IPv6 base-header nexthdr field.

Use IP6CB(skb)->iif rather than skb->skb_iif because VRF processing can
replace skb_iif with the L3 master while IP6CB keeps the receiving
interface. Preserve IP6SKB_L3SLAVE for the same reason.

Fixes: d7a669dd2f8b ("ipv6: sr: add helper functions for seg6local")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai>
Reviewed-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net: cap advertised IP tunnel headroom 2026-09-07T15:37:21+00:00 Zhiling Zou zhilinz@nebusec.ai 2026-08-12T16:22:35+00:00 9144f2c53a04465a6878172b523f640313c5559e commit 6b222adeb9340306e2ff97127c76117abb9b3df8 upstream. IP tunnel devices derive their advertised needed_headroom from lower output devices. A stack of user-created devices can make the derived value larger than the 16-bit skb header offsets can represent. Once IP output reserves it, skb head expansion can wrap those offsets. The runtime transmit path already caps a growing needed_headroom at 512. Apply the same cap when tunnel configuration publishes needed_headroom derived from a lower output device. Capping the advertised value is safe: IP tunnel transmit still expands the skb when a packet needs more headroom. A nonsensical stacked configuration can therefore incur an extra reallocation, but it cannot publish an unbounded reservation to upper layers. Fixes: 1a37e412a022 ("net: Use 16bits for *_headers fields of struct skbuff") Cc: stable@vger.kernel.org Reported-by: Vega <vega@nebusec.ai> Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Link: https://patch.msgid.link/ba04a1fd6bfae2377607fad5d8f80f7eb80fd4c4.1786542637.git.zhilinz@nebusec.ai Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 6b222adeb9340306e2ff97127c76117abb9b3df8 upstream.

IP tunnel devices derive their advertised needed_headroom from lower
output devices. A stack of user-created devices can make the derived
value larger than the 16-bit skb header offsets can represent. Once IP
output reserves it, skb head expansion can wrap those offsets.

The runtime transmit path already caps a growing needed_headroom at 512.
Apply the same cap when tunnel configuration publishes needed_headroom
derived from a lower output device.

Capping the advertised value is safe: IP tunnel transmit still expands
the skb when a packet needs more headroom. A nonsensical stacked
configuration can therefore incur an extra reallocation, but it cannot
publish an unbounded reservation to upper layers.

Fixes: 1a37e412a022 ("net: Use 16bits for *_headers fields of struct skbuff")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/ba04a1fd6bfae2377607fad5d8f80f7eb80fd4c4.1786542637.git.zhilinz@nebusec.ai
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ipv6: use RCU iterator to dump route exceptions 2026-09-07T15:36:59+00:00 Yuyang Huang sigefriedhyy@gmail.com 2026-08-15T08:46:51+00:00 f6b1b15848fd91fe122dac0d19d3d666e35075b6 commit 47cdab0d51aaa9bd85f8e4904585bd5bd4df4488 upstream. rt6_nh_dump_exceptions() uses hlist_for_each_entry() to iterate over RCU-protected exception lists. The caller holds rcu_read_lock(), but does not hold rt6_exception_lock, so rt6_insert_exception() can concurrently add an entry with hlist_add_head_rcu(). KCSAN reports this race (irrelevant details omitted): ================================================================== BUG: KCSAN: data-race in rt6_insert_exception / rt6_nh_dump_exceptions write (marked) to 0xffff8a7c44c59620 of 8 bytes by interrupt on cpu 5: rt6_insert_exception+0x3bb/0x760 __ip6_rt_update_pmtu+0x4fe/0x750 ip6_sk_update_pmtu+0x19a/0x3b0 udpv6_err+0x3ff/0x800 icmpv6_notify+0x1e1/0x440 icmpv6_rcv+0x8c0/0xab0 ip6_protocol_deliver_rcu+0x616/0x840 ip6_input_finish+0xb9/0x160 ... entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff8a7c44c59620 of 8 bytes by task 549 on cpu 14: rt6_nh_dump_exceptions+0xb3/0x260 rt6_dump_route+0x53e/0x5f0 fib6_dump_node+0x6d/0xf0 fib6_walk_continue+0x290/0x2d0 fib6_dump_table+0x28d/0x360 inet6_dump_fib+0x37d/0x620 rtnl_dumpit+0x7b/0xd0 netlink_dump+0x3ae/0x7e0 ... entry_SYSCALL_64_after_hwframe+0x77/0x7f 4 locks held by dumper/549: ... #1: (rcu_read_lock){....}-{1:3}, at: inet6_dump_fib+0x88/0x620 #2: (&tb->tb6_lock){+.-.}-{3:3}, at: fib6_dump_table+0x1e9/0x360 #3: (rcu_read_lock){....}-{1:3}, at: rt6_dump_route+0x483/0x5f0 value changed: 0xffff8a7c44e05700 -> 0xffff8a7c45d60100 Reported by Kernel Concurrency Sanitizer on: CPU: 14 UID: 0 PID: 549 Comm: dumper Not tainted 7.2.0-rc7-virtme #38 PREEMPT(lazy) ... Use hlist_for_each_entry_rcu() to safely iterate over the exception list. Fixes: 1e47b4837f3b ("ipv6: Dump route exceptions if requested") Cc: stable@vger.kernel.org Signed-off-by: Yuyang Huang <sigefriedhyy@gmail.com> Reviewed-by: Stefano Brivio <sbrivio@redhat.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Link: https://patch.msgid.link/20260815084651.69477-1-sigefriedhyy@gmail.com Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 47cdab0d51aaa9bd85f8e4904585bd5bd4df4488 upstream.

rt6_nh_dump_exceptions() uses hlist_for_each_entry() to iterate over
RCU-protected exception lists. The caller holds rcu_read_lock(), but does
not hold rt6_exception_lock, so rt6_insert_exception() can concurrently
add an entry with hlist_add_head_rcu().

KCSAN reports this race (irrelevant details omitted):

  ==================================================================
  BUG: KCSAN: data-race in rt6_insert_exception / rt6_nh_dump_exceptions

  write (marked) to 0xffff8a7c44c59620 of 8 bytes by interrupt on cpu 5:
    rt6_insert_exception+0x3bb/0x760
    __ip6_rt_update_pmtu+0x4fe/0x750
    ip6_sk_update_pmtu+0x19a/0x3b0
    udpv6_err+0x3ff/0x800
    icmpv6_notify+0x1e1/0x440
    icmpv6_rcv+0x8c0/0xab0
    ip6_protocol_deliver_rcu+0x616/0x840
    ip6_input_finish+0xb9/0x160
    ...
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

  read to 0xffff8a7c44c59620 of 8 bytes by task 549 on cpu 14:
    rt6_nh_dump_exceptions+0xb3/0x260
    rt6_dump_route+0x53e/0x5f0
    fib6_dump_node+0x6d/0xf0
    fib6_walk_continue+0x290/0x2d0
    fib6_dump_table+0x28d/0x360
    inet6_dump_fib+0x37d/0x620
    rtnl_dumpit+0x7b/0xd0
    netlink_dump+0x3ae/0x7e0
    ...
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

  4 locks held by dumper/549:
    ...
    #1: (rcu_read_lock){....}-{1:3}, at: inet6_dump_fib+0x88/0x620
    #2: (&tb->tb6_lock){+.-.}-{3:3}, at: fib6_dump_table+0x1e9/0x360
    #3: (rcu_read_lock){....}-{1:3}, at: rt6_dump_route+0x483/0x5f0

  value changed: 0xffff8a7c44e05700 -> 0xffff8a7c45d60100

  Reported by Kernel Concurrency Sanitizer on:
  CPU: 14 UID: 0 PID: 549 Comm: dumper Not tainted
  7.2.0-rc7-virtme #38 PREEMPT(lazy)
  ...

Use hlist_for_each_entry_rcu() to safely iterate over the exception list.

Fixes: 1e47b4837f3b ("ipv6: Dump route exceptions if requested")
Cc: stable@vger.kernel.org
Signed-off-by: Yuyang Huang <sigefriedhyy@gmail.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260815084651.69477-1-sigefriedhyy@gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv() 2026-09-07T15:36:59+00:00 Andrea Mayer andrea.mayer@uniroma2.it 2026-08-17T13:26:44+00:00 eab3a917cdcb182542a3aac6a0d2d30659ca9821 commit f826df95332c07380206dbd54178b6eefb311aba upstream. ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL check when reading idev->cnf.rpl_seg_enabled. When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with dev->ip6_ptr already NULL. Reproduced by flooding the receiving interface with ping6 traffic while flapping its MTU between 1500 and 1200: BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070 Read of size 4 at addr 00000000000006b4 by task ping6/394 CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full) Call Trace: <IRQ> kasan_report+0xc6/0x100 ipv6_rpl_srh_rcv+0xb3/0x1070 ip6_protocol_deliver_rcu+0x759/0x9a0 ip6_input_finish+0xa8/0x1b0 ip6_input+0xe1/0x490 ipv6_rcv+0x33d/0x460 __netif_receive_skb_one_core+0xd6/0x130 process_backlog+0x2cc/0xa00 __napi_poll.constprop.0+0x56/0x270 net_rx_action+0x327/0x730 handle_softirqs+0x11e/0x630 do_softirq+0xb3/0xf0 </IRQ> Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from ipv6_rthdr_rcv(), which already has an idev lookup. Fix the NULL dereference on the RPL path by checking idev in ipv6_rthdr_rcv(), before it calls either function. The callees take idev as an argument and no longer call __in6_dev_get(), so the packet is now dropped in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths. Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr") Cc: stable@vger.kernel.org Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it> Tested-by: Xiang Mei <xmei5@asu.edu> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260817132644.2223-1-andrea.mayer@uniroma2.it Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit f826df95332c07380206dbd54178b6eefb311aba upstream.

ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL
check when reading idev->cnf.rpl_seg_enabled.

When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears
dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev
check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with
dev->ip6_ptr already NULL.

Reproduced by flooding the receiving interface with ping6 traffic while
flapping its MTU between 1500 and 1200:

 BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070
 Read of size 4 at addr 00000000000006b4 by task ping6/394

 CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full)
 Call Trace:
  <IRQ>
  kasan_report+0xc6/0x100
  ipv6_rpl_srh_rcv+0xb3/0x1070
  ip6_protocol_deliver_rcu+0x759/0x9a0
  ip6_input_finish+0xa8/0x1b0
  ip6_input+0xe1/0x490
  ipv6_rcv+0x33d/0x460
  __netif_receive_skb_one_core+0xd6/0x130
  process_backlog+0x2cc/0xa00
  __napi_poll.constprop.0+0x56/0x270
  net_rx_action+0x327/0x730
  handle_softirqs+0x11e/0x630
  do_softirq+0xb3/0xf0
  </IRQ>

Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from
ipv6_rthdr_rcv(), which already has an idev lookup.

Fix the NULL dereference on the RPL path by checking idev in
ipv6_rthdr_rcv(), before it calls either function. The callees take idev as
an argument and no longer call __in6_dev_get(), so the packet is now
dropped in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths.

Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr")
Cc: stable@vger.kernel.org
Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Tested-by: Xiang Mei <xmei5@asu.edu>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260817132644.2223-1-andrea.mayer@uniroma2.it
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ip6_gre: fix hardware header length for NBMA tunnels 2026-09-07T15:36:58+00:00 Zhiling Zou zhilinz@nebusec.ai 2026-08-12T16:22:34+00:00 565038b0092f65afe384961c0f548d605bf438b9 commit 505b6d296c486ef7d1274f279d4c43a172f63224 upstream. ip6gre_tnl_link_config_route() accumulates the lower device's hardware header length into dev->hard_header_len whenever header_ops is set. This is incorrect for both users of header_ops. ip6gretap and ip6erspan have a fixed Ethernet hardware header length. For an NBMA ip6gre tunnel, ip6gre_header() creates only the GRE header, the optional FOU or GUE header, and the outer IPv6 header. The lower device header is headroom needed later, not part of the tunnel device's hardware header. Keep the lower device header in needed_headroom. Set hard_header_len to the tunnel header length only for ARPHRD_IP6GRE devices with header_ops, and leave the fixed Ethernet header length unchanged for tap and erspan devices. Fixes: 832ba596494b ("net: ip6_gre: set dev->hard_header_len when using header_ops") Cc: stable@vger.kernel.org Suggested-by: Ido Schimmel <idosch@nvidia.com> Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Link: https://patch.msgid.link/64b46542bbe1701f07702aaa50273e2a87903db5.1786542637.git.zhilinz@nebusec.ai Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 505b6d296c486ef7d1274f279d4c43a172f63224 upstream.

ip6gre_tnl_link_config_route() accumulates the lower device's hardware
header length into dev->hard_header_len whenever header_ops is set. This
is incorrect for both users of header_ops.

ip6gretap and ip6erspan have a fixed Ethernet hardware header length.
For an NBMA ip6gre tunnel, ip6gre_header() creates only the GRE header,
the optional FOU or GUE header, and the outer IPv6 header. The lower
device header is headroom needed later, not part of the tunnel device's
hardware header.

Keep the lower device header in needed_headroom. Set hard_header_len to
the tunnel header length only for ARPHRD_IP6GRE devices with header_ops,
and leave the fixed Ethernet header length unchanged for tap and erspan
devices.

Fixes: 832ba596494b ("net: ip6_gre: set dev->hard_header_len when using header_ops")
Cc: stable@vger.kernel.org
Suggested-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/64b46542bbe1701f07702aaa50273e2a87903db5.1786542637.git.zhilinz@nebusec.ai
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>