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Message-Id: <1275487236-14452-1-git-send-email-xiaosuo@gmail.com>
Date: Wed, 2 Jun 2010 22:00:36 +0800
From: Changli Gao <xiaosuo@...il.com>
To: Jamal Hadi Salim <hadi@...erus.ca>
Cc: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
Changli Gao <xiaosuo@...il.com>
Subject: [PATCH v2] cls_u32: use skb_header_pointer() to dereference data safely
use skb_header_pointer() to dereference data safely
the original skb->data dereference isn't safe, as there isn't any skb->len or
skb_is_nonlinear() check. skb_header_pointer() is used instead in this patch.
And when the skb isn't long enough, we terminate the function u32_classify()
immediately with -1. Unaligned access is also fixed.
Signed-off-by: Changli Gao <xiaosuo@...il.com>
----
net/sched/cls_u32.c | 51 ++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 38 insertions(+), 13 deletions(-)
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 9627542..e6dba22 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -41,6 +41,7 @@
#include <net/netlink.h>
#include <net/act_api.h>
#include <net/pkt_cls.h>
+#include <asm/unaligned.h>
struct tc_u_knode
{
@@ -98,11 +99,11 @@ static int u32_classify(struct sk_buff *skb, struct tcf_proto *tp, struct tcf_re
{
struct {
struct tc_u_knode *knode;
- u8 *ptr;
+ unsigned int off;
} stack[TC_U32_MAXDEPTH];
struct tc_u_hnode *ht = (struct tc_u_hnode*)tp->root;
- u8 *ptr = skb_network_header(skb);
+ unsigned int off = skb_network_header(skb) - skb->data;
struct tc_u_knode *n;
int sdepth = 0;
int off2 = 0;
@@ -134,8 +135,14 @@ next_knode:
#endif
for (i = n->sel.nkeys; i>0; i--, key++) {
-
- if ((*(__be32*)(ptr+key->off+(off2&key->offmask))^key->val)&key->mask) {
+ unsigned int toff;
+ __be32 *data, _data;
+
+ toff = off + key->off + (off2 & key->offmask);
+ data = skb_header_pointer(skb, toff, 4, &_data);
+ if (!data)
+ goto out;
+ if ((get_unaligned(data) ^ key->val) & key->mask) {
n = n->next;
goto next_knode;
}
@@ -174,29 +181,46 @@ check_terminal:
if (sdepth >= TC_U32_MAXDEPTH)
goto deadloop;
stack[sdepth].knode = n;
- stack[sdepth].ptr = ptr;
+ stack[sdepth].off = off;
sdepth++;
ht = n->ht_down;
sel = 0;
- if (ht->divisor)
- sel = ht->divisor&u32_hash_fold(*(__be32*)(ptr+n->sel.hoff), &n->sel,n->fshift);
-
+ if (ht->divisor) {
+ __be32 *data, _data;
+
+ data = skb_header_pointer(skb, off + n->sel.hoff, 4,
+ &_data);
+ if (!data)
+ goto out;
+ sel = ht->divisor & u32_hash_fold(get_unaligned(data),
+ &n->sel, n->fshift);
+ }
if (!(n->sel.flags&(TC_U32_VAROFFSET|TC_U32_OFFSET|TC_U32_EAT)))
goto next_ht;
if (n->sel.flags&(TC_U32_OFFSET|TC_U32_VAROFFSET)) {
off2 = n->sel.off + 3;
- if (n->sel.flags&TC_U32_VAROFFSET)
- off2 += ntohs(n->sel.offmask & *(__be16*)(ptr+n->sel.offoff)) >>n->sel.offshift;
+ if (n->sel.flags & TC_U32_VAROFFSET) {
+ __be16 *data, _data;
+
+ data = skb_header_pointer(skb,
+ off + n->sel.offoff,
+ 2, &_data);
+ if (!data)
+ goto out;
+ off2 += ntohs(n->sel.offmask &
+ get_unaligned(data)) >>
+ n->sel.offshift;
+ }
off2 &= ~3;
}
if (n->sel.flags&TC_U32_EAT) {
- ptr += off2;
+ off += off2;
off2 = 0;
}
- if (ptr < skb_tail_pointer(skb))
+ if (off < skb->len)
goto next_ht;
}
@@ -204,9 +228,10 @@ check_terminal:
if (sdepth--) {
n = stack[sdepth].knode;
ht = n->ht_up;
- ptr = stack[sdepth].ptr;
+ off = stack[sdepth].off;
goto check_terminal;
}
+out:
return -1;
deadloop:
--
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