linux-kernel - [PATCH 5.11 383/601] block/rnbd-clt-sysfs: Remove copy buffer overlap in rnbd_clt_get_path

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Date:   Wed, 12 May 2021 16:47:40 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dima Stepanov <dmitrii.stepanov@...os.com>,
        Arnd Bergmann <arnd@...db.de>,
        Jack Wang <jinpu.wang@...os.com>,
        Gioh Kim <gi-oh.kim@...ud.ionos.com>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 383/601] block/rnbd-clt-sysfs: Remove copy buffer overlap in rnbd_clt_get_path_name

From: Dima Stepanov <dmitrii.stepanov@...ud.ionos.com>

[ Upstream commit 3db7cf55d532a15ea26b4a14e8f8729ccd96fd22 ]

cppcheck report the following error:
  rnbd/rnbd-clt-sysfs.c:522:36: error: The variable 'buf' is used both
  as a parameter and as destination in snprintf(). The origin and
  destination buffers overlap. Quote from glibc (C-library)
  documentation
  (http://www.gnu.org/software/libc/manual/html_mono/libc.html#Formatted-Output-Functions):
  "If copying takes place between objects that overlap as a result of a
  call to sprintf() or snprintf(), the results are undefined."
  [sprintfOverlappingData]
Fix it by initializing the buf variable in the first snprintf call.

Fixes: 91f4acb2801c ("block/rnbd-clt: support mapping two devices")
Signed-off-by: Dima Stepanov <dmitrii.stepanov@...os.com>
Cc: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Jack Wang <jinpu.wang@...os.com>
Signed-off-by: Gioh Kim <gi-oh.kim@...ud.ionos.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@....com>
Link: https://lore.kernel.org/r/20210419073722.15351-19-gi-oh.kim@ionos.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/block/rnbd/rnbd-clt-sysfs.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/block/rnbd/rnbd-clt-sysfs.c b/drivers/block/rnbd/rnbd-clt-sysfs.c
index 526c77cd7a50..49ad400a5225 100644
--- a/drivers/block/rnbd/rnbd-clt-sysfs.c
+++ b/drivers/block/rnbd/rnbd-clt-sysfs.c
@@ -483,11 +483,7 @@ static int rnbd_clt_get_path_name(struct rnbd_clt_dev *dev, char *buf,
 	while ((s = strchr(pathname, '/')))
 		s[0] = '!';
 
-	ret = snprintf(buf, len, "%s", pathname);
-	if (ret >= len)
-		return -ENAMETOOLONG;
-
-	ret = snprintf(buf, len, "%s@%s", buf, dev->sess->sessname);
+	ret = snprintf(buf, len, "%s@%s", pathname, dev->sess->sessname);
 	if (ret >= len)
 		return -ENAMETOOLONG;
 
-- 
2.30.2