On Tue, 21 Nov 2006, Jesper Juhl wrote:
> Any reason why we can't apply the patch below?
>
> On 30/10/06, Jesper Juhl <[email protected]> wrote:
> >
> > There's a potential problem in isdn_ppp.c::isdn_ppp_decompress().
> > dev_alloc_skb() may fail and return NULL. If it does we will be passing a
> > NULL skb_out to ipc->decompress() and may also end up
> > dereferencing a NULL pointer at
> > *proto = isdn_ppp_strip_proto(skb_out);
> > Correct this by testing 'skb_out' against NULL early and bail out.
> >
> >
> > Signed-off-by: Jesper Juhl <[email protected]>
> > ---
> >
> > drivers/isdn/i4l/isdn_ppp.c | 5 +++++
> > 1 files changed, 5 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/isdn/i4l/isdn_ppp.c b/drivers/isdn/i4l/isdn_ppp.c
> > index 119412d..5a97ce6 100644
> > --- a/drivers/isdn/i4l/isdn_ppp.c
> > +++ b/drivers/isdn/i4l/isdn_ppp.c
> > @@ -2536,6 +2536,11 @@ static struct sk_buff *isdn_ppp_decompre
> > rsparm.maxdlen = IPPP_RESET_MAXDATABYTES;
> >
> > skb_out = dev_alloc_skb(is->mru + PPP_HDRLEN);
> > + if (!skb_out) {
> > + kfree_skb(skb);
> > + printk(KERN_ERR "ippp: decomp memory allocation
> > failure\n");
> > + return NULL;
> > + }
> > len = ipc->decompress(stat, skb, skb_out, &rsparm);
> > kfree_skb(skb);
> > if (len <= 0) {
> >
>
I'm not sure that there's a problem with the original code. If skb_out
cannot be allocated, the ipc->decompress function should return NULL
because struct ippp_struct *master would have been passed as NULL. So len
would be 0 upon return, skb would be freed, and the following switch
statement would catch the error. Notice it's not a bug to pass NULL to
kfree_skb() later.
David
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