phonet/pep: disable BH around forwarded sk_receive_skb()

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Summary

CVECVE-2026-64177
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:59 UTC
Updated2026-07-19 16:17:59 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: phonet/pep: disable BH around forwarded sk_receive_skb() The networking receive path is usually run from softirq context, but protocols that take the socket lock may have packets stored in the backlog and processed later from process context. In that case release_sock() -> __release_sock() drops the slock with spin_unlock_bh() and then calls sk->sk_backlog_rcv() with bottom halves enabled. Typical sk_backlog_rcv handlers process the socket whose backlog is being drained, so the BH state at entry is irrelevant for the slocks they touch. pep_do_rcv() is different: when the inbound skb targets an existing PEP pipe, it forwards the skb to a different *child* socket via sk_receive_skb(). That helper takes the child slock with bh_lock_sock_nested(), which is just spin_lock_nested() and assumes BH is already off. The same child slock therefore ends up acquired with BH on (process path) and with BH off (softirq path): process context softirq context --------------- --------------- release_sock(listener) __netif_receive_skb() __release_sock() phonet_rcv() spin_unlock_bh() __sk_receive_skb(listener) [BH now ENABLED] [BH already disabled] sk_backlog_rcv: sk_backlog_rcv: pep_do_rcv() pep_do_rcv() sk_receive_skb(child) sk_receive_skb(child) bh_lock_sock_nested(child) bh_lock_sock_nested(child) => SOFTIRQ-ON-W => IN-SOFTIRQ-W Lockdep flags this as inconsistent lock state, and it can become a real self-deadlock if a softirq on the same CPU tries to receive to the same child socket while its slock is held in the BH-enabled path: WARNING: inconsistent lock state inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. (slock-AF_PHONET/1){+.?.}-{3:3}, at: __sk_receive_skb+0x1cf/0x900 __sk_receive_skb net/core/sock.c:563 sk_receive_skb include/net/sock.h:2022 [inline] pep_do_rcv net/phonet/pep.c:675 sk_backlog_rcv include/net/sock.h:1190 __release_sock net/core/sock.c:3216 release_sock net/core/sock.c:3815 pep_sock_accept net/phonet/pep.c:879 Wrap the forwarded sk_receive_skb() in local_bh_disable() / local_bh_enable() so the child slock is always acquired with BH off. local_bh_disable() nests safely on the softirq path. Discovered via in-house syzkaller fuzzing; the same root cause also on the linux-6.1.y syzbot dashboard as extid 44f0626dd6284f02663c. Reproduced under KASAN + LOCKDEP + PROVE_LOCKING, reproducer: https://pastebin.com/A3t8xzCR

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 9641458d3ec42def729fde64669abf07f3220cd5 f08c45076e4fd8b0adbc5eb186d6e6a3e7350d7b git Not specified
CNA Linux Linux affected 9641458d3ec42def729fde64669abf07f3220cd5 b2606c302d7f2b4ee48da05e32ed60aed1b0cd53 git Not specified
CNA Linux Linux affected 9641458d3ec42def729fde64669abf07f3220cd5 02c04df84de709060f63e1d52ec67488c4f6f212 git Not specified
CNA Linux Linux affected 9641458d3ec42def729fde64669abf07f3220cd5 8420aa4900417797323dd567ba9d1512280c2dc3 git Not specified
CNA Linux Linux affected 9641458d3ec42def729fde64669abf07f3220cd5 bd795f106b3889fb0706c6e4831c4b27e2b5666b git Not specified
CNA Linux Linux affected 9641458d3ec42def729fde64669abf07f3220cd5 84bc87beb4cd77670939b446326788e4c9b3db37 git Not specified
CNA Linux Linux affected 9641458d3ec42def729fde64669abf07f3220cd5 a3fc8f2dacd1c37325977fc1fbbf3d52141df99e git Not specified
CNA Linux Linux affected 9641458d3ec42def729fde64669abf07f3220cd5 dbc81608e3a653dea6cf403f20cae35468b8ab9c git Not specified
CNA Linux Linux affected 2.6.28 Not specified
CNA Linux Linux unaffected 2.6.28 semver Not specified
CNA Linux Linux unaffected 5.10.258 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.209 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.175 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.142 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.92 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.34 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.11 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/dbc81608e3a653dea6cf403f20cae35468b8ab9c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b2606c302d7f2b4ee48da05e32ed60aed1b0cd53 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a3fc8f2dacd1c37325977fc1fbbf3d52141df99e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8420aa4900417797323dd567ba9d1512280c2dc3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/02c04df84de709060f63e1d52ec67488c4f6f212 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bd795f106b3889fb0706c6e4831c4b27e2b5666b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/84bc87beb4cd77670939b446326788e4c9b3db37 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f08c45076e4fd8b0adbc5eb186d6e6a3e7350d7b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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