Hi,
In drivers/isdn/hisax/isdnl2.c:l2_pull_iqueue() we have this:
...
skb = alloc_skb(oskb->len + i, GFP_ATOMIC);
memcpy(skb_put(skb, i), header, i);
...
If alloc_skb() fails and returns NULL then the second line will cause a
NULL pointer dereference - skb_put() gives the pointer to
skb_tail_pointer() which dereferences it.
I'm not quite sure how this should be dealt with, so I'll just report it
rather than submit a patch. Happy bug fixing :-)
--
Jesper Juhl <[email protected]> http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please.
From: Jesper Juhl <[email protected]>
Date: Thu, 3 Feb 2011 21:27:56 +0100 (CET)
> In drivers/isdn/hisax/isdnl2.c:l2_pull_iqueue() we have this:
>
> ...
> skb = alloc_skb(oskb->len + i, GFP_ATOMIC);
> memcpy(skb_put(skb, i), header, i);
> ...
>
> If alloc_skb() fails and returns NULL then the second line will cause a
> NULL pointer dereference - skb_put() gives the pointer to
> skb_tail_pointer() which dereferences it.
>
> I'm not quite sure how this should be dealt with, so I'll just report it
> rather than submit a patch. Happy bug fixing :-)
Thanks Jesper, I'll fix this like so:
--------------------
hisax: Fix unchecked alloc_skb() return.
Jesper Juhl noticed that l2_pull_iqueue() does not
check to see if alloc_skb() fails.
Fix this by first trying to reallocate the headroom
if necessary, rather than later after we've made hard
to undo state changes.
Reported-by: Jesper Juhl <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
---
drivers/isdn/hisax/isdnl2.c | 35 ++++++++++++++++++++---------------
1 files changed, 20 insertions(+), 15 deletions(-)
diff --git a/drivers/isdn/hisax/isdnl2.c b/drivers/isdn/hisax/isdnl2.c
index 0858791..98ac835 100644
--- a/drivers/isdn/hisax/isdnl2.c
+++ b/drivers/isdn/hisax/isdnl2.c
@@ -1243,14 +1243,21 @@ l2_st7_tout_203(struct FsmInst *fi, int event, void *arg)
st->l2.rc = 0;
}
+static int l2_hdr_space_needed(struct Layer2 *l2)
+{
+ int len = test_bit(FLG_LAPD, &l2->flag) ? 2 : 1;
+
+ return len + (test_bit(FLG_LAPD, &l2->flag) ? 2 : 1);
+}
+
static void
l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
{
struct PStack *st = fi->userdata;
- struct sk_buff *skb, *oskb;
+ struct sk_buff *skb;
struct Layer2 *l2 = &st->l2;
u_char header[MAX_HEADER_LEN];
- int i;
+ int i, hdr_space_needed;
int unsigned p1;
u_long flags;
@@ -1261,6 +1268,16 @@ l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
if (!skb)
return;
+ hdr_space_needed = l2_hdr_space_needed(l2);
+ if (hdr_space_needed > skb_headroom(skb)) {
+ struct sk_buff *orig_skb = skb;
+
+ skb = skb_realloc_headroom(skb, hdr_space_needed);
+ if (!skb) {
+ dev_kfree_skb(orig_skb);
+ return;
+ }
+ }
spin_lock_irqsave(&l2->lock, flags);
if(test_bit(FLG_MOD128, &l2->flag))
p1 = (l2->vs - l2->va) % 128;
@@ -1285,19 +1302,7 @@ l2_pull_iqueue(struct FsmInst *fi, int event, void *arg)
l2->vs = (l2->vs + 1) % 8;
}
spin_unlock_irqrestore(&l2->lock, flags);
- p1 = skb->data - skb->head;
- if (p1 >= i)
- memcpy(skb_push(skb, i), header, i);
- else {
- printk(KERN_WARNING
- "isdl2 pull_iqueue skb header(%d/%d) too short\n", i, p1);
- oskb = skb;
- skb = alloc_skb(oskb->len + i, GFP_ATOMIC);
- memcpy(skb_put(skb, i), header, i);
- skb_copy_from_linear_data(oskb,
- skb_put(skb, oskb->len), oskb->len);
- dev_kfree_skb(oskb);
- }
+ memcpy(skb_push(skb, i), header, i);
st->l2.l2l1(st, PH_PULL | INDICATION, skb);
test_and_clear_bit(FLG_ACK_PEND, &st->l2.flag);
if (!test_and_set_bit(FLG_T200_RUN, &st->l2.flag)) {
--
1.7.4.1
On Mon, 14 Feb 2011 00:53:09 -0000, Dave Miler wrote:
> From: Jesper Juhl <[email protected]>
>
> > In drivers/isdn/hisax/isdnl2.c:l2_pull_iqueue() we have this:
> >
> > ...
> > skb = alloc_skb(oskb->len + i, GFP_ATOMIC);
> > memcpy(skb_put(skb, i), header, i);
> > ...
> >
> > If alloc_skb() fails and returns NULL then the second line will cause a
> > NULL pointer dereference - skb_put() gives the pointer to
> > skb_tail_pointer() which dereferences it.
> >
> > I'm not quite sure how this should be dealt with, so I'll just report it
> > rather than submit a patch. Happy bug fixing :-)
>
> Thanks Jesper, I'll fix this like so:
>
> --------------------
> hisax: Fix unchecked alloc_skb() return.
>
> Jesper Juhl noticed that l2_pull_iqueue() does not
> check to see if alloc_skb() fails.
>
> Fix this by first trying to reallocate the headroom
> if necessary, rather than later after we've made hard
> to undo state changes.
>
> Reported-by: Jesper Juhl <[email protected]>
> Signed-off-by: David S. Miller <[email protected]>
>
> ---
> drivers/isdn/hisax/isdnl2.c | 35 ++++++++++++++++++++---------------
> 1 files changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/isdn/hisax/isdnl2.c b/drivers/isdn/hisax/isdnl2.c
> index 0858791..98ac835 100644
> --- a/drivers/isdn/hisax/isdnl2.c
> +++ b/drivers/isdn/hisax/isdnl2.c
> @@ -1243,14 +1243,21 @@ l2_st7_tout_203(struct FsmInst *fi, int event, void *arg)
> st->l2.rc = 0;
> }
>
> +static int l2_hdr_space_needed(struct Layer2 *l2)
> +{
> + int len = test_bit(FLG_LAPD, &l2->flag) ? 2 : 1;
> +
> + return len + (test_bit(FLG_LAPD, &l2->flag) ? 2 : 1);
> +}
> +
That struck me as an funny way to write 2 * len, so I finally looked
at the code. I think one of those should be FLG_MOD128, but then
at that point why not use the existing l2headersize(l2, ui) with
ui = 0?
I see this is in linux-next of Feb 15, 2011.
milton
From: Milton Miller <[email protected]>
Date: Tue, 15 Feb 2011 14:09:16 -0600
> On Mon, 14 Feb 2011 00:53:09 -0000, Dave Miler wrote:
>> diff --git a/drivers/isdn/hisax/isdnl2.c b/drivers/isdn/hisax/isdnl2.c
>> index 0858791..98ac835 100644
>> --- a/drivers/isdn/hisax/isdnl2.c
>> +++ b/drivers/isdn/hisax/isdnl2.c
>> @@ -1243,14 +1243,21 @@ l2_st7_tout_203(struct FsmInst *fi, int event, void *arg)
>> st->l2.rc = 0;
>> }
>>
>> +static int l2_hdr_space_needed(struct Layer2 *l2)
>> +{
>> + int len = test_bit(FLG_LAPD, &l2->flag) ? 2 : 1;
>> +
>> + return len + (test_bit(FLG_LAPD, &l2->flag) ? 2 : 1);
>> +}
>> +
>
> That struck me as an funny way to write 2 * len, so I finally looked
> at the code. I think one of those should be FLG_MOD128, but then
> at that point why not use the existing l2headersize(l2, ui) with
> ui = 0?
>
> I see this is in linux-next of Feb 15, 2011.
Good catch, thanks. I'll fix this.