io_uring: handle setup-failed ctx in kill_timeouts
general protection fault, probably for non-canonical address
0xdffffc0000000018: 0000 [#1] KASAN: null-ptr-deref
in range [0x00000000000000c0-0x00000000000000c7]
RIP: 0010:io_commit_cqring+0x37f/0xc10 fs/io_uring.c:1318
Call Trace:
io_kill_timeouts+0x2b5/0x320 fs/io_uring.c:8606
io_ring_ctx_wait_and_kill+0x1da/0x400 fs/io_uring.c:8629
io_uring_create fs/io_uring.c:9572 [inline]
io_uring_setup+0x10da/0x2ae0 fs/io_uring.c:9599
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
It can get into wait_and_kill() before setting up ctx->rings, and hence
io_commit_cqring() fails. Mimic poll cancel and do it only when we
completed events, there can't be any requests if it failed before
initialising rings.
Fixes: 80c4cbdb5ee60 ("io_uring: do post-completion chore on t-out cancel")
Reported-by: syzbot+0e905eb8228070c457a0@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/660261a48f0e7abf260c8e43c87edab3c16736fa.1617014345.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index a4a944d..088a9d3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8603,9 +8603,9 @@ static bool io_kill_timeouts(struct io_ring_ctx *ctx, struct task_struct *tsk,
canceled++;
}
}
- io_commit_cqring(ctx);
+ if (canceled != 0)
+ io_commit_cqring(ctx);
spin_unlock_irq(&ctx->completion_lock);
-
if (canceled != 0)
io_cqring_ev_posted(ctx);
return canceled != 0;