From fd6c2e4c063d64511657ad0031a1677b6a914859 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Wed, 18 Dec 2019 12:19:41 -0700
Subject: io_uring: io_wq_submit_work() should not touch req->rw

I've been chasing a weird and obscure crash that was userspace stack
corruption, and finally narrowed it down to a bit flip that made a
stack address invalid. io_wq_submit_work() unconditionally flips
the req->rw.ki_flags IOCB_NOWAIT bit, but since it's a generic work
handler, this isn't valid. Normal read/write operations own that
part of the request, on other types it could be something else.

Move the IOCB_NOWAIT clear to the read/write handlers where it belongs.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

(limited to 'fs/io_uring.c')

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 81e7fe6dee18..6f084e3cf835 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1817,6 +1817,10 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
 			return ret;
 	}
 
+	/* Ensure we clear previously set non-block flag */
+	if (!force_nonblock)
+		req->rw.ki_flags &= ~IOCB_NOWAIT;
+
 	file = req->file;
 	io_size = ret;
 	if (req->flags & REQ_F_LINK)
@@ -1906,6 +1910,10 @@ static int io_write(struct io_kiocb *req, struct io_kiocb **nxt,
 			return ret;
 	}
 
+	/* Ensure we clear previously set non-block flag */
+	if (!force_nonblock)
+		req->rw.ki_flags &= ~IOCB_NOWAIT;
+
 	file = kiocb->ki_filp;
 	io_size = ret;
 	if (req->flags & REQ_F_LINK)
@@ -3274,9 +3282,6 @@ static void io_wq_submit_work(struct io_wq_work **workptr)
 	struct io_kiocb *nxt = NULL;
 	int ret = 0;
 
-	/* Ensure we clear previously set non-block flag */
-	req->rw.ki_flags &= ~IOCB_NOWAIT;
-
 	if (work->flags & IO_WQ_WORK_CANCEL)
 		ret = -ECANCELED;
 
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