CVE-2026-53035

Summary

In the Linux kernel, the following vulnerability has been resolved:

bpf, sockmap: Fix af_unix iter deadlock

bpf_iter_unix_seq_show() may deadlock when lock_sock_fast() takes the fast path and the iter prog attempts to update a sockmap. Which ends up spinning at sock_map_update_elem()'s bh_lock_sock():

WARNING: possible recursive locking detected test_progs/1393 is trying to acquire lock: ffff88811ec25f58 (slock-AF_UNIX){+…}-{3:3}, at: sock_map_update_elem+0xdb/0x1f0

but task is already holding lock: ffff88811ec25f58 (slock-AF_UNIX){+…}-{3:3}, at: __lock_sock_fast+0x37/0xe0

other info that might help us debug this: Possible unsafe locking scenario:

   CPU0
   ----

lock(slock-AF_UNIX); lock(slock-AF_UNIX);

*** DEADLOCK ***

May be due to missing lock nesting notation

4 locks held by test_progs/1393: #0: ffff88814b59c790 (&p->lock){+.+.}-{4:4}, at: bpf_seq_read+0x59/0x10d0 #1: ffff88811ec25fd8 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: bpf_seq_read+0x42c/0x10d0 #2: ffff88811ec25f58 (slock-AF_UNIX){+…}-{3:3}, at: __lock_sock_fast+0x37/0xe0 #3: ffffffff85a6a7c0 (rcu_read_lock){….}-{1:3}, at: bpf_iter_run_prog+0x51d/0xb00

Call Trace: dump_stack_lvl+0x5d/0x80 print_deadlock_bug.cold+0xc0/0xce __lock_acquire+0x130f/0x2590 lock_acquire+0x14e/0x2b0 _raw_spin_lock+0x30/0x40 sock_map_update_elem+0xdb/0x1f0 bpf_prog_2d0075e5d9b721cd_dump_unix+0x55/0x4f4 bpf_iter_run_prog+0x5b9/0xb00 bpf_iter_unix_seq_show+0x1f7/0x2e0 bpf_seq_read+0x42c/0x10d0 vfs_read+0x171/0xb20 ksys_read+0xff/0x200 do_syscall_64+0x6b/0x3a0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/bd3592129f24243713673a07225cf1f15a9bb835
• https://git.kernel.org/stable/c/3cef33b9813b78f227942572fb317afcd5c9ac94
• https://git.kernel.org/stable/c/87828b380956d4986f59f2c086e0b09b3e6cdaae
• https://git.kernel.org/stable/c/527057ebe8076dfbcaef51195ff1b7508646be2c
• https://git.kernel.org/stable/c/66d9fab4565eafe1afe7ba0581f79b76073b60fa
• https://git.kernel.org/stable/c/4d328dd695383224aa750ddee6b4ad40c0f8d205

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