[PATCH 3.16 017/148] ar5523: check NULL before memcpy() in ar5523_cmd()

[Ben Hutchings]

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

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

From: Denis Efremov <efremov@xxxxxxxxx>

commit 315cee426f87658a6799815845788fde965ddaad upstream.

memcpy() call with "idata == NULL && ilen == 0" results in undefined
behavior in ar5523_cmd(). For example, NULL is passed in callchain
"ar5523_stat_work() -> ar5523_cmd_write() -> ar5523_cmd()". This patch
adds ilen check before memcpy() call in ar5523_cmd() to prevent an
undefined behavior.

Cc: Pontus Fuchs <pontus.fuchs@xxxxxxxxx>
Cc: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Signed-off-by: Denis Efremov <efremov@xxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/net/wireless/ath/ar5523/ar5523.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/wireless/ath/ar5523/ar5523.c
+++ b/drivers/net/wireless/ath/ar5523/ar5523.c
@@ -255,7 +255,8 @@ static int ar5523_cmd(struct ar5523 *ar,
 
 	if (flags & AR5523_CMD_FLAG_MAGIC)
 		hdr->magic = cpu_to_be32(1 << 24);
-	memcpy(hdr + 1, idata, ilen);
+	if (ilen)
+		memcpy(hdr + 1, idata, ilen);
 
 	cmd->odata = odata;
 	cmd->olen = olen;