[PATCH][ISDN] fix possible NULL deref on low memory condition in capidrv.c::send_message()

[Jesper Juhl <jesper.juhl@gmail.com>]

If we fail to allocate an skb in 
drivers/isdn/capi/capidrv.c::send_message(), then we'll end up 
dereferencing a NULL pointer.
Since out of memory conditions are not unheard of, I believe it 
is better to print a error message and just return rather than 
bring down the whole kernel. 
Sure, doing this may upset some application, but that's still 
better than crashing the whole system.

(ps. please Cc me on replies from the isdn4linux list since I'm not subscribed 
 there)


Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
---

 drivers/isdn/capi/capidrv.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/isdn/capi/capidrv.c b/drivers/isdn/capi/capidrv.c
index 23b6f7b..476012b 100644
--- a/drivers/isdn/capi/capidrv.c
+++ b/drivers/isdn/capi/capidrv.c
@@ -506,9 +506,14 @@ static void send_message(capidrv_contr * card, _cmsg * cmsg)
 {
 	struct sk_buff *skb;
 	size_t len;
+
 	capi_cmsg2message(cmsg, cmsg->buf);
 	len = CAPIMSG_LEN(cmsg->buf);
 	skb = alloc_skb(len, GFP_ATOMIC);
+	if (!skb) {
+		printk(KERN_ERR "capidrv::send_message: can't allocate mem\n");
+		return;
+	}
 	memcpy(skb_put(skb, len), cmsg->buf, len);
 	if (capi20_put_message(&global.ap, skb) != CAPI_NOERROR)
 		kfree_skb(skb);
-
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