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Message-ID: <457894.1682352358@warthog.procyon.org.uk> Date: Mon, 24 Apr 2023 17:05:58 +0100 From: David Howells <dhowells@...hat.com> To: Dmitry Vyukov <dvyukov@...gle.com> Cc: dhowells@...hat.com, syzbot <syzbot+ebc945fdb4acd72cba78@...kaller.appspotmail.com>, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, linux-afs@...ts.infradead.org, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, marc.dionne@...istor.com, netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com Subject: Re: [syzbot] [afs?] [net?] KCSAN: data-race in rxrpc_send_data / rxrpc_set_call_completion Dmitry Vyukov <dvyukov@...gle.com> wrote: > If I am reading this correctly, rxrpc_send_data() can read wrong > call->completion and state and incorrectly exit with an error if > rxrpc_wait_to_be_connected() exists early right after observing error > set here: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/rxrpc/sendmsg.c?id=148341f0a2f53b5e8808d093333d85170586a15d#n58 > The code seems to assume that at that point all writes done by > rxrpc_set_call_completion() are already finished, but it's not > necessarily the case. I'm not sure it matters. call->error can only be set by the I/O thread and only if a call fails - in which case the call state will be set shortly thereafter - plus a couple of places where we fail to set the call up, in which case we're under the call's user_mutex or didn't even manage to fully allocate it. That said, I probably should check the call state first. I might also want to ignore any signal if the call did manage to get connected, lest I leave it dangling - a problem might come if userspace issues a single sendmsg() to set up the call and supply data to be transmitted. I need to have a ponder on that one. David
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