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From: Ammar Faizi <[email protected]>
To: Jens Axboe <[email protected]>
Cc: GNU/Weeb Mailing List <[email protected]>,
	io-uring Mailing list <[email protected]>,
	Tea Inside Mailing List <[email protected]>,
	Linux Kernel Mailing List <[email protected]>,
	Alviro Iskandar Setiawan <[email protected]>,
	kernel test robot <[email protected]>,
	Dan Carpenter <[email protected]>,
	"Chen, Rong A" <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Ammar Faizi <[email protected]>
Subject: [PATCH io_uring-5.17] io_uring: Fix build error potential reading uninitialized value
Date: Mon,  7 Feb 2022 18:43:15 +0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

From: Alviro Iskandar Setiawan <[email protected]>

In io_recv() if import_single_range() fails, the @flags variable is
uninitialized, then it will goto out_free.

After the goto, the compiler doesn't know that (ret < min_ret) is
always true, so it thinks the "if ((flags & MSG_WAITALL) ..."  path
could be taken.

The complaint comes from gcc-9 (Debian 9.3.0-22) 9.3.0:
```
  fs/io_uring.c:5238 io_recvfrom() error: uninitialized symbol 'flags'
```
Fix this by bypassing the @ret and @flags check when
import_single_range() fails.

Reasons:
 1. import_single_range() only returns -EFAULT when it fails.
 2. At that point @flags is uninitialized and shouldn't be read.

Reported-by: kernel test robot <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Reported-by: "Chen, Rong A" <[email protected]>
Link: https://lore.gnuweeb.org/timl/[email protected]/
Cc: Pavel Begunkov <[email protected]>
Suggested-by: Ammar Faizi <[email protected]>
Fixes: 7297ce3d59449de49d3c9e1f64ae25488750a1fc ("io_uring: improve send/recv error handling")
Signed-off-by: Alviro Iskandar Setiawan <[email protected]>
Signed-off-by: Ammar Faizi <[email protected]>
---
 fs/io_uring.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 2e04f718319d..3445c4da0153 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5228,7 +5228,6 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 		min_ret = iov_iter_count(&msg.msg_iter);
 
 	ret = sock_recvmsg(sock, &msg, flags);
-out_free:
 	if (ret < min_ret) {
 		if (ret == -EAGAIN && force_nonblock)
 			return -EAGAIN;
@@ -5236,9 +5235,9 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 			ret = -EINTR;
 		req_set_fail(req);
 	} else if ((flags & MSG_WAITALL) && (msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC))) {
+out_free:
 		req_set_fail(req);
 	}
-
 	__io_req_complete(req, issue_flags, ret, io_put_kbuf(req));
 	return 0;
 }

base-commit: f6133fbd373811066c8441737e65f384c8f31974
-- 
2.32.0


       reply	other threads:[~2022-02-07 13:07 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <[email protected]>
2022-02-07 11:43 ` Ammar Faizi [this message]
2022-02-07 13:45   ` [PATCH io_uring-5.17] io_uring: Fix build error potential reading uninitialized value Jens Axboe
2022-02-07 14:05     ` [PATCH io_uring-5.17 v2] io_uring: Clean up a false-positive warning from GCC 9.3.0 Ammar Faizi
2022-02-07 15:38       ` Jens Axboe
2022-02-07 14:20     ` [PATCH io_uring-5.17] io_uring: Fix build error potential reading uninitialized value Dan Carpenter
2022-02-07 14:33       ` Alviro Iskandar Setiawan
2022-02-07 15:37         ` Jens Axboe

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