linux-kernel - [PATCH 3.16 18/99] altera-stapl: check for a null key before strcasecmp'ing it

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Message-ID: <lsq.1554212307.367424539@decadent.org.uk>
Date:   Tue, 02 Apr 2019 14:38:27 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Colin Ian King" <colin.king@...onical.com>
Subject: [PATCH 3.16 18/99] altera-stapl: check for a null key before
 strcasecmp'ing it

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

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

From: Colin Ian King <colin.king@...onical.com>

commit 9ccb645683ef46e3c52c12c088a368baa58447d4 upstream.

Currently the null check on key is occurring after the strcasecmp on
the key, hence there is a potential null pointer dereference on key.
Fix this by checking if key is null first. Also replace the == 0
check on strcasecmp with just the ! operator.

Detected by CoverityScan, CID#1248787 ("Dereference before null check")

Fixes: fa766c9be58b ("[media] Altera FPGA firmware download module")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: old code used strnicmp()]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/misc/altera-stapl/altera.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/misc/altera-stapl/altera.c b/drivers/misc/altera-stapl/altera.c
index ef83a9078646..d2ed3b9728b7 100644
--- a/drivers/misc/altera-stapl/altera.c
+++ b/drivers/misc/altera-stapl/altera.c
@@ -2176,8 +2176,7 @@ static int altera_get_note(u8 *p, s32 program_size,
 			key_ptr = &p[note_strings +
 					get_unaligned_be32(
 					&p[note_table + (8 * i)])];
-			if ((strnicmp(key, key_ptr, strlen(key_ptr)) == 0) &&
-						(key != NULL)) {
+			if (key && !strncasecmp(key, key_ptr, strlen(key_ptr))) {
 				status = 0;
 
 				value_ptr = &p[note_strings +