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net/smc: protect clcsock lifetime in smc_getname

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smc_getname() dereferences smc->clcsock without holding
clcsock_release_lock. Link-group termination can release the CLC socket
through smc_close_active_abort() while the SMC socket is still open,
for example after shutdown(SHUT_WR).

A getsockname() caller can load smc->clcsock, then the termination worker
can clear the pointer and call sock_release() before the caller accesses
clcsock->ops or invokes getname(). This causes a use-after-free; if the
worker clears the pointer before the load, it causes a NULL dereference.
The syscall's file reference keeps the SMC socket alive but does not
prevent asynchronous release of its CLC socket.

KASAN reported the following with test-only timing instrumentation:

  BUG: KASAN: slab-use-after-free in smc_getname+0x19e/0x1b0
  Read of size 8 at addr ffff888109abb4e0 by task poc/103
  Call Trace:
   smc_getname+0x19e/0x1b0
   do_getsockname+0xe5/0x170
   __sys_getsockname+0x8c/0x100

  Allocated by task 95:
   sock_alloc_inode+0x1e/0x280
   sock_alloc+0x3d/0x240
   __sock_create+0x7e/0x430
   smc_create+0x121/0x240

  Freed by task 0:
   kmem_cache_free+0xcc/0x340
   rcu_core+0x50a/0x1850

  Last potentially related work creation:
   evict+0x446/0x6c0
   smc_clcsock_release+0xa8/0xd0
   smc_close_active_abort+0x26a/0x3a0
   __smc_lgr_terminate.part.0+0x137/0x2e0

Hold clcsock_release_lock across the pointer check and the getname()
callback to serialize with smc_clcsock_release(). Return -EBADF if the
CLC socket has already been released, preserving the existing peer
state check and the callback's return value otherwise.

Fixes: b03faa1faf ("net/smc: postpone release of clcsock")
Cc: stable@vger.kernel.org
Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>
Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Link: https://patch.msgid.link/20261008084444.787449-1-nicoyip.dev@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Chengfeng Ye 2026-10-08 16:44:44 +08:00 • committed by Jakub Kicinski
commit 64a6b36b0e
1 changed files with 6 additions and 1 deletions
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