2007-08-04 18:36:41

by Jesper Juhl

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

(first send: Monday 25 June 2007, resending due to no response)
(resending again since there has still been no response)


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 <[email protected]>
---

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);

2007-08-06 12:06:04

by Karsten Keil

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

On Sat, Aug 04, 2007 at 08:31:37PM +0200, Jesper Juhl wrote:
> (first send: Monday 25 June 2007, resending due to no response)
> (resending again since there has still been no response)
>
>
> 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 <[email protected]>

Acked-by: Karsten Keil <[email protected]>

> ---
>
> 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);
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/

--
Karsten Keil
SuSE Labs
ISDN and VOIP development
SUSE LINUX Products GmbH, Maxfeldstr.5 90409 Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg)