Re: [PATCH net v3] net/smc: protect clcsock lifetime in smc_getname

[sashiko-bot@kernel.org]

> 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
> [ ... ]
> 
> Fixes: b03faa1fafc8 ("net/smc: postpone release of clcsock")
> Cc: stable@vger.kernel.org
> Assisted-by: GPT-6.1-Sol
> Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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