3.11.10.11 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Mathias Krause <[email protected]> commit 05ab8f2647e4221cbdb3856dd7d32bd5407316b3 upstream. 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 <[email protected]> Cc: Pablo Neira Ayuso <[email protected]> Signed-off-by: Mathias Krause <[email protected]> Acked-by: Daniel Borkmann <[email protected]> Signed-off-by: David S. Miller <[email protected]> [ luis: backported to 3.11: used davem's backport to 3.10 ] Signed-off-by: Luis Henriques <[email protected]> --- net/core/filter.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/core/filter.c b/net/core/filter.c index 52f01229ee01..c6c18d8a2d88 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -355,6 +355,8 @@ 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; @@ -371,11 +373,13 @@ 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); -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
