diff options
Diffstat (limited to 'trunk/2.6.18/debian-security-patches/appletalk-length-mismatch.patch')
| -rw-r--r-- | trunk/2.6.18/debian-security-patches/appletalk-length-mismatch.patch | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/trunk/2.6.18/debian-security-patches/appletalk-length-mismatch.patch b/trunk/2.6.18/debian-security-patches/appletalk-length-mismatch.patch new file mode 100644 index 0000000..b82c4fe --- /dev/null +++ b/trunk/2.6.18/debian-security-patches/appletalk-length-mismatch.patch @@ -0,0 +1,93 @@ +From: Jean Delvare <jdelvare@suse.de> +Date: Thu, 5 Apr 2007 06:52:46 +0000 (-0700) +Subject: [APPLETALK]: Fix a remotely triggerable crash +X-Git-Tag: v2.6.21-rc6~3 +X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=75559c167bddc1254db5bcff032ad5eed8bd6f4a + +[APPLETALK]: Fix a remotely triggerable crash + +When we receive an AppleTalk frame shorter than what its header says, +we still attempt to verify its checksum, and trip on the BUG_ON() at +the end of function atalk_sum_skb() because of the length mismatch. + +This has security implications because this can be triggered by simply +sending a specially crafted ethernet frame to a target victim, +effectively crashing that host. Thus this qualifies, I think, as a +remote DoS. Here is the frame I used to trigger the crash, in npg +format: + +<Appletalk Killer> +{ +# Ethernet header ----- + + XX XX XX XX XX XX # Destination MAC + 00 00 00 00 00 00 # Source MAC + 00 1D # Length + +# LLC header ----- + + AA AA 03 + 08 00 07 80 9B # Appletalk + +# Appletalk header ----- + + 00 1B # Packet length (invalid) + 00 01 # Fake checksum + 00 00 00 00 # Destination and source networks + 00 00 00 00 # Destination and source nodes and ports + +# Payload ----- + + 0C 0D 0E 0F 10 11 12 13 + 14 +} + +The destination MAC address must be set to those of the victim. + +The severity is mitigated by two requirements: +* The target host must have the appletalk kernel module loaded. I + suspect this isn't so frequent. +* AppleTalk frames are non-IP, thus I guess they can only travel on + local networks. I am no network expert though, maybe it is possible + to somehow encapsulate AppleTalk packets over IP. + +The bug has been reported back in June 2004: + http://bugzilla.kernel.org/show_bug.cgi?id=2979 +But it wasn't investigated, and was closed in July 2006 as both +reporters had vanished meanwhile. + +This code was new in kernel 2.6.0-test5: + http://git.kernel.org/?p=linux/kernel/git/tglx/history.git;a=commitdiff;h=7ab442d7e0a76402c12553ee256f756097cae2d2 +And not modified since then, so we can assume that vanilla kernels +2.6.0-test5 and later, and distribution kernels based thereon, are +affected. + +Note that I still do not know for sure what triggered the bug in the +real-world cases. The frame could have been corrupted by the kernel if +we have a bug hiding somewhere. But more likely, we are receiving the +faulty frame from the network. + +Signed-off-by: Jean Delvare <jdelvare@suse.de> +Signed-off-by: David S. Miller <davem@davemloft.net> +--- + +diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c +index 113c175..c8b7dc2 100644 +--- a/net/appletalk/ddp.c ++++ b/net/appletalk/ddp.c +@@ -1417,10 +1417,13 @@ static int atalk_rcv(struct sk_buff *skb, struct net_device *dev, + /* + * Size check to see if ddp->deh_len was crap + * (Otherwise we'll detonate most spectacularly +- * in the middle of recvmsg()). ++ * in the middle of atalk_checksum() or recvmsg()). + */ +- if (skb->len < sizeof(*ddp)) ++ if (skb->len < sizeof(*ddp) || skb->len < (len_hops & 1023)) { ++ pr_debug("AppleTalk: dropping corrupted frame (deh_len=%u, " ++ "skb->len=%u)\n", len_hops & 1023, skb->len); + goto freeit; ++ } + + /* + * Any checksums. Note we don't do htons() on this == is assumed to be |