From 51520426f4bc3e61cbbf7a39ccf4e411b665002d Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Mon, 29 Mar 2021 11:39:29 +0100 Subject: 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 Link: https://lore.kernel.org/r/660261a48f0e7abf260c8e43c87edab3c16736fa.1617014345.git.asml.silence@gmail.com Signed-off-by: Jens Axboe --- fs/io_uring.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs') diff --git a/fs/io_uring.c b/fs/io_uring.c index a4a944da95a0..088a9d3c420a 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; -- cgit v1.2.3