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Date:   Fri, 21 Jan 2022 21:06:52 +0800
From:   Wen Gu <>
Subject: Re: [PATCH net v2] net/smc: Transitional solution for clcsock race

On 2022/1/21 8:43 pm, Wen Gu wrote:
> We encountered a crash in smc_setsockopt() and it is caused by
> accessing smc->clcsock after clcsock was released.
>   BUG: kernel NULL pointer dereference, address: 0000000000000020
>   #PF: supervisor read access in kernel mode
>   #PF: error_code(0x0000) - not-present page
>   PGD 0 P4D 0
>   Oops: 0000 [#1] PREEMPT SMP PTI
>   CPU: 1 PID: 50309 Comm: nginx Kdump: loaded Tainted: G E     5.16.0-rc4+ #53
>   RIP: 0010:smc_setsockopt+0x59/0x280 [smc]
>   Call Trace:
>    <TASK>
>    __sys_setsockopt+0xfc/0x190
>    __x64_sys_setsockopt+0x20/0x30
>    do_syscall_64+0x34/0x90
>    entry_SYSCALL_64_after_hwframe+0x44/0xae
>   RIP: 0033:0x7f16ba83918e
>    </TASK>
> This patch tries to fix it by holding clcsock_release_lock and
> checking whether clcsock has already been released before access.
> In case that a crash of the same reason happens in smc_getsockopt()
> or smc_switch_to_fallback(), this patch also checkes smc->clcsock
> in them too. And the caller of smc_switch_to_fallback() will identify
> whether fallback succeeds according to the return value.
> Fixes: fd57770dd198 ("net/smc: wait for pending work before clcsock release_sock")
> Link:
> Signed-off-by: Wen Gu <>
> Acked-by: Karsten Graul <>
> ---

I seem to have missed this:

v2 -> v1:

Add 'Fixes:' tag and 'Link:' tag.

Looks like I need a script to check the details to avoid mistake...

Wen Gu

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