linux-kernel - [PATCH 3.16 117/133] IB/mlx4: fix sprintf format warning

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Date:   Wed, 22 Nov 2017 01:58:13 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Leon Romanovsky" <leonro@...lanox.com>,
        "Arnd Bergmann" <arnd@...db.de>
Subject: [PATCH 3.16 117/133] IB/mlx4: fix sprintf format warning

3.16.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@...db.de>

commit d0dbf771309fecd73f4ac1566c1400cb12807ee2 upstream.

gcc-7 points out that a negative port_num value would overflow the
string buffer:

  drivers/infiniband/hw/mlx4/sysfs.c: In function 'mlx4_ib_device_register_sysfs':
  drivers/infiniband/hw/mlx4/sysfs.c:251:16: error: 'sprintf' may write a terminating nul past the end of the destination [-Werror=format-overflow=]
  drivers/infiniband/hw/mlx4/sysfs.c:251:2: note: 'sprintf' output between 2 and 11 bytes into a destination of size 10
  drivers/infiniband/hw/mlx4/sysfs.c:303:17: error: 'sprintf' may write a terminating nul past the end of the destination [-Werror=format-overflow=]
  drivers/infiniband/hw/mlx4/sysfs.c:303:3: note: 'sprintf' output between 2 and 11 bytes into a destination of size 10

While we should be able to assume that port_num is positive here, making
the buffer one byte longer has no downsides and avoids the warning.

Fixes: c1e7e466120b ("IB/mlx4: Add iov directory in sysfs under the ib device")
Link: http://lkml.kernel.org/r/20170714120720.906842-23-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Leon Romanovsky <leonro@...lanox.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/infiniband/hw/mlx4/sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/hw/mlx4/sysfs.c
+++ b/drivers/infiniband/hw/mlx4/sysfs.c
@@ -241,7 +241,7 @@ void del_sysfs_port_mcg_attr(struct mlx4
 static int add_port_entries(struct mlx4_ib_dev *device, int port_num)
 {
 	int i;
-	char buff[10];
+	char buff[11];
 	struct mlx4_ib_iov_port *port = NULL;
 	int ret = 0 ;
 	struct ib_port_attr attr;