[PATCH v2 2/2] io_uring: don't submit half-prepared drain request

[Pavel Begunkov <asml.silence@gmail.com>]

[ 3784.910888] BUG: kernel NULL pointer dereference, address: 0000000000000020
[ 3784.910904] RIP: 0010:__io_file_supports_nowait+0x5/0xc0
[ 3784.910926] Call Trace:
[ 3784.910928]  ? io_read+0x17c/0x480
[ 3784.910945]  io_issue_sqe+0xcb/0x1840
[ 3784.910953]  __io_queue_sqe+0x44/0x300
[ 3784.910959]  io_req_task_submit+0x27/0x70
[ 3784.910962]  tctx_task_work+0xeb/0x1d0
[ 3784.910966]  task_work_run+0x61/0xa0
[ 3784.910968]  io_run_task_work_sig+0x53/0xa0
[ 3784.910975]  __x64_sys_io_uring_enter+0x22/0x30
[ 3784.910977]  do_syscall_64+0x3d/0x90
[ 3784.910981]  entry_SYSCALL_64_after_hwframe+0x44/0xae

io_drain_req() goes before checks for REQ_F_FAIL, which protect us from
submitting under-prepared request (e.g. failed in io_init_req(). Fail
such drained requests as well.

Fixes: a8295b982c46d ("io_uring: fix failed linkchain code logic")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6e07456d9842..2514adced460 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6232,6 +6232,11 @@ static bool io_drain_req(struct io_kiocb *req)
 	int ret;
 	u32 seq;
 
+	if (req->flags & REQ_F_FAIL) {
+		io_req_complete_fail_submit(req);
+		return true;
+	}
+
 	/*
 	 * If we need to drain a request in the middle of a link, drain the
 	 * head request and the next request/link after the current link.
-- 
2.33.0