isdn/gigaset: fix zero size border case in debug dump

[ 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@oracle.com>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/isdn/gigaset/capi.c b/drivers/isdn/gigaset/capi.c
index fd17bb3..08c2329 100644 (file)
--- 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;