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CVE-2017-5897 ip6_gre: Invalid reads in ip6gre_err (rhbz 1419848 1419851)

This commit is contained in:
Justin M. Forbes 2017-02-07 08:15:40 -06:00
parent 08749d8479
commit 8843cd40ee
2 changed files with 97 additions and 0 deletions
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91
ip6_gre-fix-ip6gre_err-invalid-reads.patch Normal file
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@ -0,0 +1,91 @@
From 7892032cfe67f4bde6fc2ee967e45a8fbaf33756 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Sat, 4 Feb 2017 23:18:55 -0800
Subject: ip6_gre: fix ip6gre_err() invalid reads
Andrey Konovalov reported out of bound accesses in ip6gre_err()
If GRE flags contains GRE_KEY, the following expression
*(((__be32 *)p) + (grehlen / 4) - 1)
accesses data ~40 bytes after the expected point, since
grehlen includes the size of IPv6 headers.
Let's use a "struct gre_base_hdr *greh" pointer to make this
code more readable.
p[1] becomes greh->protocol.
grhlen is the GRE header length.
Fixes: c12b395a4664 ("gre: Support GRE over IPv6")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/ipv6/ip6_gre.c | 40 +++++++++++++++++++++-------------------
1 file changed, 21 insertions(+), 19 deletions(-)
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 5586318..630b73b 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -367,35 +367,37 @@ static void ip6gre_tunnel_uninit(struct net_device *dev)
static void ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
- u8 type, u8 code, int offset, __be32 info)
+ u8 type, u8 code, int offset, __be32 info)
{
- const struct ipv6hdr *ipv6h = (const struct ipv6hdr *)skb->data;
- __be16 *p = (__be16 *)(skb->data + offset);
- int grehlen = offset + 4;
+ const struct gre_base_hdr *greh;
+ const struct ipv6hdr *ipv6h;
+ int grehlen = sizeof(*greh);
struct ip6_tnl *t;
+ int key_off = 0;
__be16 flags;
+ __be32 key;
- flags = p[0];
- if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
- if (flags&(GRE_VERSION|GRE_ROUTING))
- return;
- if (flags&GRE_KEY) {
- grehlen += 4;
- if (flags&GRE_CSUM)
- grehlen += 4;
- }
+ if (!pskb_may_pull(skb, offset + grehlen))
+ return;
+ greh = (const struct gre_base_hdr *)(skb->data + offset);
+ flags = greh->flags;
+ if (flags & (GRE_VERSION | GRE_ROUTING))
+ return;
+ if (flags & GRE_CSUM)
+ grehlen += 4;
+ if (flags & GRE_KEY) {
+ key_off = grehlen + offset;
+ grehlen += 4;
}
- /* If only 8 bytes returned, keyed message will be dropped here */
- if (!pskb_may_pull(skb, grehlen))
+ if (!pskb_may_pull(skb, offset + grehlen))
return;
ipv6h = (const struct ipv6hdr *)skb->data;
- p = (__be16 *)(skb->data + offset);
+ greh = (const struct gre_base_hdr *)(skb->data + offset);
+ key = key_off ? *(__be32 *)(skb->data + key_off) : 0;
t = ip6gre_tunnel_lookup(skb->dev, &ipv6h->daddr, &ipv6h->saddr,
- flags & GRE_KEY ?
- *(((__be32 *)p) + (grehlen / 4) - 1) : 0,
- p[1]);
+ key, greh->protocol);
if (!t)
return;
--
cgit v0.12

6
kernel.spec
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@ -640,6 +640,9 @@ Patch855: kvm-fix-page-struct-leak-in-handle_vmon.patch
# rhbz 1418858
Patch856: PCI-ASPM-Handle-PCI-to-PCIe-bridges-as-roots-of-PCIe-hierarchies.patch
#CVE-2017-5897 rhbz 1419848 1419851
Patch857: ip6_gre-fix-ip6gre_err-invalid-reads.patch
# END OF PATCH DEFINITIONS
%endif
@ -2187,6 +2190,9 @@ fi
#
#
%changelog
* Tue Feb 7 2017 Justin M. Forbes <jforbes@fedoraproject.org>
- CVE-2017-5897 ip6_gre: Invalid reads in ip6gre_err (rhbz 1419848 1419851)
* Tue Feb 7 2017 Peter Robinson <pbrobinson@fedoraproject.org> 4.9.8-201
- Drop "fixes" for bcm238x as they seem to break other Raspberry Pi 3 things