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Date: Fri, 21 Jan 2022 21:06:52 +0800 From: Wen Gu <guwen@...ux.alibaba.com> To: kgraul@...ux.ibm.com, davem@...emloft.net, kuba@...nel.org Cc: linux-s390@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH net v2] net/smc: Transitional solution for clcsock race issue 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: https://lore.kernel.org/lkml/5dd7ffd1-28e2-24cc-9442-1defec27375e@linux.ibm.com/T/ > Signed-off-by: Wen Gu <guwen@...ux.alibaba.com> > Acked-by: Karsten Graul <kgraul@...ux.ibm.com> > --- 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... Thanks, Wen Gu
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