* potential null pointer dereference in drivers/isdn/hisax/isdnl2.c @ 2011-02-03 20:27 Jesper Juhl 2011-02-14 0:53 ` David Miller 0 siblings, 1 reply; 4+ messages in thread From: Jesper Juhl @ 2011-02-03 20:27 UTC (permalink / raw) To: linux-kernel; +Cc: netdev, Tejun Heo, Karsten Keil 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 <jj@chaosbits.net> http://www.chaosbits.net/ Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: potential null pointer dereference in drivers/isdn/hisax/isdnl2.c 2011-02-03 20:27 potential null pointer dereference in drivers/isdn/hisax/isdnl2.c Jesper Juhl @ 2011-02-14 0:53 ` David Miller 2011-02-15 20:09 ` Milton Miller 0 siblings, 1 reply; 4+ messages in thread From: David Miller @ 2011-02-14 0:53 UTC (permalink / raw) To: jj; +Cc: linux-kernel, netdev, tj, isdn From: Jesper Juhl <jj@chaosbits.net> 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 <jj@chaosbits.net> Signed-off-by: David S. Miller <davem@davemloft.net> --- 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 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: potential null pointer dereference in drivers/isdn/hisax/isdnl2.c 2011-02-14 0:53 ` David Miller @ 2011-02-15 20:09 ` Milton Miller 2011-02-15 20:15 ` David Miller 0 siblings, 1 reply; 4+ messages in thread From: Milton Miller @ 2011-02-15 20:09 UTC (permalink / raw) To: David Miller; +Cc: linux-kernel, netdev, tj, isdn, jj On Mon, 14 Feb 2011 00:53:09 -0000, Dave Miler wrote: > From: Jesper Juhl <jj@chaosbits.net> > > > 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 <jj@chaosbits.net> > Signed-off-by: David S. Miller <davem@davemloft.net> > > --- > 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 ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: potential null pointer dereference in drivers/isdn/hisax/isdnl2.c 2011-02-15 20:09 ` Milton Miller @ 2011-02-15 20:15 ` David Miller 0 siblings, 0 replies; 4+ messages in thread From: David Miller @ 2011-02-15 20:15 UTC (permalink / raw) To: miltonm; +Cc: linux-kernel, netdev, tj, isdn, jj From: Milton Miller <miltonm@bga.com> 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. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2011-02-15 20:15 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2011-02-03 20:27 potential null pointer dereference in drivers/isdn/hisax/isdnl2.c Jesper Juhl 2011-02-14 0:53 ` David Miller 2011-02-15 20:09 ` Milton Miller 2011-02-15 20:15 ` David Miller
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