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io_uring: io_wq_submit_work() should not touch req->rw

PATCH New Jens Axboe 1 participant 1 message Dec 18, 2019

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Jens Axboe

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PATCH 1/1 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 <[email protected]>

---

This one was fun to find, random flip of a bit in an unrelated struct...

fs/io_uring.c +8 -3
index b7800def3090..b632bd9222d9 100644
@@ -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)

@@ -3272,9 +3280,6 @@ 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;
Signature · 1 line
Jens Axboe