[ 45/66] isdn/gigaset: fix zero size border case in debug dump

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Tilman Schmidt <tilman@xxxxxxx>

[ Upstream commit d721a1752ba544df8d7d36959038b26bc92bdf80 ]

If subtracting 12 from l leaves zero we'd do a zero size allocation,
leading to an oops later when we try to set the NUL terminator.

Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Tilman Schmidt <tilman@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/isdn/gigaset/capi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/isdn/gigaset/capi.c b/drivers/isdn/gigaset/capi.c
index fd17bb3..08c2329 100644
--- a/drivers/isdn/gigaset/capi.c
+++ b/drivers/isdn/gigaset/capi.c
@@ -264,6 +264,8 @@ static inline void dump_rawmsg(enum debuglevel level, const char *tag,
 		CAPIMSG_APPID(data), CAPIMSG_MSGID(data), l,
 		CAPIMSG_CONTROL(data));
 	l -= 12;
+	if (l <= 0)
+		return;
 	dbgline = kmalloc(3*l, GFP_ATOMIC);
 	if (!dbgline)
 		return;


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