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Date: Tue, 10 Aug 2021 23:20:24 +0900 From: asmadeus@...ewreck.org To: Leon Romanovsky <leon@...nel.org> Cc: Tuo Li <islituo@...il.com>, ericvh@...il.com, lucho@...kov.net, davem@...emloft.net, kuba@...nel.org, v9fs-developer@...ts.sourceforge.net, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, baijiaju1990@...il.com, TOTE Robot <oslab@...nghua.edu.cn> Subject: Re: [PATCH] net: 9p: Fix possible null-pointer dereference in p9_cm_event_handler() Leon Romanovsky wrote on Tue, Aug 10, 2021 at 04:55:42PM +0300: > On Tue, Aug 10, 2021 at 06:20:07AM -0700, Tuo Li wrote: > > The variable rdma is checked when event->event is equal to > > RDMA_CM_EVENT_DISCONNECTED: > > if (rdma) > > > > This indicates that it can be NULL. If so, a null-pointer dereference will > > occur when calling complete(): > > complete(&rdma->cm_done); > > > > To fix this possible null-pointer dereference, calling complete() only > > when rdma is not NULL. > > You need to explain how is it possible and blindly set if () checks. > I would say first "if (rdma)" is not needed, but don't know for sure. Sounds like static analysis because there's a if (rdma) check in RDMA_CM_EVENT_DISCONNECTED above, so if that needed check then it will bug right afterwards I'd tend to agree I don't think it's possible client->trans is null there (it's filled right after rdma_create_id which defines the handler, there might be a window where the callback is called before? But as I understand it shouldn't be called until we resolve address and connect then later disconnect) So, I agree with Leon - unless you have a backtrace of a real bug let's remove the other 'if' if you want to cleanup something for your robot. -- Dominique
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