diff options
| author | Mathias Krause <minipli@googlemail.com> | 2014-04-13 18:23:33 +0200 |
|---|---|---|
| committer | Stefan Bader <stefan.bader@canonical.com> | 2014-11-25 15:20:24 +0100 |
| commit | 5e80f87653161a5b4f177fb300ed72eeb76520e7 (patch) | |
| tree | 1918d36623deb4ee3be1cbcf6d2be145c2ea02cc | |
| parent | 58a833121ab00981b7a364f8a836ad67ddaa3147 (diff) | |
| download | linux-2.6.32.y-drm33.z-5e80f87653161a5b4f177fb300ed72eeb76520e7.tar.gz | |
filter: prevent nla extensions to peek beyond the end of the message
[ Upstream commit 05ab8f2647e4221cbdb3856dd7d32bd5407316b3 ]
The BPF_S_ANC_NLATTR and BPF_S_ANC_NLATTR_NEST extensions fail to check
for a minimal message length before testing the supplied offset to be
within the bounds of the message. This allows the subtraction of the nla
header to underflow and therefore -- as the data type is unsigned --
allowing far to big offset and length values for the search of the
netlink attribute.
The remainder calculation for the BPF_S_ANC_NLATTR_NEST extension is
also wrong. It has the minuend and subtrahend mixed up, therefore
calculates a huge length value, allowing to overrun the end of the
message while looking for the netlink attribute.
The following three BPF snippets will trigger the bugs when attached to
a UNIX datagram socket and parsing a message with length 1, 2 or 3.
,-[ PoC for missing size check in BPF_S_ANC_NLATTR ]--
| ld #0x87654321
| ldx #42
| ld #nla
| ret a
`---
,-[ PoC for the same bug in BPF_S_ANC_NLATTR_NEST ]--
| ld #0x87654321
| ldx #42
| ld #nlan
| ret a
`---
,-[ PoC for wrong remainder calculation in BPF_S_ANC_NLATTR_NEST ]--
| ; (needs a fake netlink header at offset 0)
| ld #0
| ldx #42
| ld #nlan
| ret a
`---
Fix the first issue by ensuring the message length fulfills the minimal
size constrains of a nla header. Fix the second bug by getting the math
for the remainder calculation right.
Fixes: 4738c1db15 ("[SKFILTER]: Add SKF_ADF_NLATTR instruction")
Fixes: d214c7537b ("filter: add SKF_AD_NLATTR_NEST to look for nested..")
Cc: Patrick McHardy <kaber@trash.net>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[geissert: backport to 2.6.32]
[wt: fixes CVE-2014-3144]
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
| -rw-r--r-- | net/core/filter.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index d162169b88fd0b..a2dcdb94e0fcf3 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -316,6 +316,9 @@ load_b: if (skb_is_nonlinear(skb)) return 0; + if (skb->len < sizeof(struct nlattr)) + return 0; + if (A > skb->len - sizeof(struct nlattr)) return 0; @@ -332,11 +335,14 @@ load_b: if (skb_is_nonlinear(skb)) return 0; + if (skb->len < sizeof(struct nlattr)) + return 0; + if (A > skb->len - sizeof(struct nlattr)) return 0; nla = (struct nlattr *)&skb->data[A]; - if (nla->nla_len > A - skb->len) + if (nla->nla_len > skb->len - A) return 0; nla = nla_find_nested(nla, X); |