| Message ID | 20161127155815.10359-1-amir@vadai.me |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On Sun, Nov 27, 2016 at 7:58 AM, Amir Vadai <amir@vadai.me> wrote: > Should not allow setting a negative offset that goes below the skb head. ... > diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c > index b54d56d4959b..e79e8a88f2d2 100644 > --- a/net/sched/act_pedit.c > +++ b/net/sched/act_pedit.c > @@ -154,8 +154,11 @@ static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a, > } > > ptr = skb_header_pointer(skb, off + offset, 4, &_data); > - if (!ptr) > + if ((unsigned char *)ptr < skb->head) { ptr returned could be &_data, which is on stack, so why this comparison makes sense for this case? > + pr_info("tc filter pedit offset out of bounds\n"); > goto bad; > + } > + > /* just do it, baby */ > *ptr = ((*ptr & tkey->mask) ^ tkey->val); > if (ptr == &_data) > -- > 2.10.2 >
From: Cong Wang <xiyou.wangcong@gmail.com> Date: Sun, 27 Nov 2016 21:39:33 -0800 > On Sun, Nov 27, 2016 at 7:58 AM, Amir Vadai <amir@vadai.me> wrote: >> Should not allow setting a negative offset that goes below the skb head. > ... >> diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c >> index b54d56d4959b..e79e8a88f2d2 100644 >> --- a/net/sched/act_pedit.c >> +++ b/net/sched/act_pedit.c >> @@ -154,8 +154,11 @@ static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a, >> } >> >> ptr = skb_header_pointer(skb, off + offset, 4, &_data); >> - if (!ptr) >> + if ((unsigned char *)ptr < skb->head) { > > > ptr returned could be &_data, which is on stack, so why this comparison > makes sense for this case? Indeed, this will definitely do the wrong thing when the on-stack area passed back to ptr.
On Mon, Nov 28, 2016 at 12:49:36AM -0500, David Miller wrote: > From: Cong Wang <xiyou.wangcong@gmail.com> > Date: Sun, 27 Nov 2016 21:39:33 -0800 > > > On Sun, Nov 27, 2016 at 7:58 AM, Amir Vadai <amir@vadai.me> wrote: > >> Should not allow setting a negative offset that goes below the skb head. > > ... > >> diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c > >> index b54d56d4959b..e79e8a88f2d2 100644 > >> --- a/net/sched/act_pedit.c > >> +++ b/net/sched/act_pedit.c > >> @@ -154,8 +154,11 @@ static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a, > >> } > >> > >> ptr = skb_header_pointer(skb, off + offset, 4, &_data); > >> - if (!ptr) > >> + if ((unsigned char *)ptr < skb->head) { > > > > > > ptr returned could be &_data, which is on stack, so why this comparison > > makes sense for this case? > > Indeed, this will definitely do the wrong thing when the on-stack area > passed back to ptr. yes - my bad. will correct it and send v1
diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c index b54d56d4959b..e79e8a88f2d2 100644 --- a/net/sched/act_pedit.c +++ b/net/sched/act_pedit.c @@ -154,8 +154,11 @@ static int tcf_pedit(struct sk_buff *skb, const struct tc_action *a, } ptr = skb_header_pointer(skb, off + offset, 4, &_data); - if (!ptr) + if ((unsigned char *)ptr < skb->head) { + pr_info("tc filter pedit offset out of bounds\n"); goto bad; + } + /* just do it, baby */ *ptr = ((*ptr & tkey->mask) ^ tkey->val); if (ptr == &_data)
Should not allow setting a negative offset that goes below the skb head. Signed-off-by: Amir Vadai <amir@vadai.me> --- Hi Dave, Please pull to -stable branches. Thanks, Amir net/sched/act_pedit.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)