[PATCH 5.10 16/95] netfilter: ip6t_rt: fix rt0_hdr parsing in rt_mt6

Greg Kroah-Hartman
2021-10-25T19:36:46Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit a482c5e00a9b5a194085bcd372ac36141028becb ]

In rt_mt6(), when it's a nonlinear skb, the 1st skb_header_pointer()
only copies sizeof(struct ipv6_rt_hdr) to _route that rh points to.
The access by ((const struct rt0_hdr *)rh)->reserved will overflow
the buffer. So this access should be moved below the 2nd call to
skb_header_pointer().

Besides, after the 2nd skb_header_pointer(), its return value should
also be checked, othersize, *rp may cause null-pointer-ref.

v1->v2:
- clean up some old debugging log.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/netfilter/ip6t_rt.c | 48 +++++-------------------------------
1 file changed, 6 insertions(+), 42 deletions(-)

diff --git a/net/ipv6/netfilter/ip6t_rt.c b/net/ipv6/netfilter/ip6t_rt.c
index 733c83d38b30..4ad8b2032f1f 100644
--- a/net/ipv6/netfilter/ip6t_rt.c
+++ b/net/ipv6/netfilter/ip6t_rt.c
@@ -25,12 +25,7 @@ MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
static inline bool
segsleft_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
{
- bool r;
- pr_debug("segsleft_match:%c 0x%x <= 0x%x <= 0x%x\n",
- invert ? '!' : ' ', min, id, max);
- r = (id >= min && id <= max) ^ invert;
- pr_debug(" result %s\n", r ? "PASS" : "FAILED");
- return r;
+ return (id >= min && id <= max) ^ invert;
}

static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
@@ -65,30 +60,6 @@ static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
return false;
}

- pr_debug("IPv6 RT LEN %u %u ", hdrlen, rh->hdrlen);
- pr_debug("TYPE %04X ", rh->type);
- pr_debug("SGS_LEFT %u %02X\n", rh->segments_left, rh->segments_left);
-
- pr_debug("IPv6 RT segsleft %02X ",
- segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
- rh->segments_left,
- !!(rtinfo->invflags & IP6T_RT_INV_SGS)));
- pr_debug("type %02X %02X %02X ",
- rtinfo->rt_type, rh->type,
- (!(rtinfo->flags & IP6T_RT_TYP) ||
- ((rtinfo->rt_type == rh->type) ^
- !!(rtinfo->invflags & IP6T_RT_INV_TYP))));
- pr_debug("len %02X %04X %02X ",
- rtinfo->hdrlen, hdrlen,
- !(rtinfo->flags & IP6T_RT_LEN) ||
- ((rtinfo->hdrlen == hdrlen) ^
- !!(rtinfo->invflags & IP6T_RT_INV_LEN)));
- pr_debug("res %02X %02X %02X ",
- rtinfo->flags & IP6T_RT_RES,
- ((const struct rt0_hdr *)rh)->reserved,
- !((rtinfo->flags & IP6T_RT_RES) &&
- (((const struct rt0_hdr *)rh)->reserved)));
-
ret = (segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
rh->segments_left,
!!(rtinfo->invflags & IP6T_RT_INV_SGS))) &&
@@ -107,22 +78,22 @@ static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
reserved),
sizeof(_reserved),
&_reserved);
+ if (!rp) {
+ par->hotdrop = true;
+ return false;
+ }

ret = (*rp == 0);
}

- pr_debug("#%d ", rtinfo->addrnr);
if (!(rtinfo->flags & IP6T_RT_FST)) {
return ret;
} else if (rtinfo->flags & IP6T_RT_FST_NSTRICT) {
- pr_debug("Not strict ");
if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
- pr_debug("There isn't enough space\n");
return false;
} else {
unsigned int i = 0;

- pr_debug("#%d ", rtinfo->addrnr);
for (temp = 0;
temp < (unsigned int)((hdrlen - 8) / 16);
temp++) {
@@ -138,26 +109,20 @@ static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
return false;
}

- if (ipv6_addr_equal(ap, &rtinfo->addrs[i])) {
- pr_debug("i=%d temp=%d;\n", i, temp);
+ if (ipv6_addr_equal(ap, &rtinfo->addrs[i]))
i++;
- }
if (i == rtinfo->addrnr)
break;
}
- pr_debug("i=%d #%d\n", i, rtinfo->addrnr);
if (i == rtinfo->addrnr)
return ret;
else
return false;
}
} else {
- pr_debug("Strict ");
if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
- pr_debug("There isn't enough space\n");
return false;
} else {
- pr_debug("#%d ", rtinfo->addrnr);
for (temp = 0; temp < rtinfo->addrnr; temp++) {
ap = skb_header_pointer(skb,
ptr
@@ -173,7 +138,6 @@ static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
if (!ipv6_addr_equal(ap, &rtinfo->addrs[temp]))
break;
}
- pr_debug("temp=%d #%d\n", temp, rtinfo->addrnr);
if (temp == rtinfo->addrnr &&
temp == (unsigned int)((hdrlen - 8) / 16))
return ret;
--
2.33.0