[PATCH 3.10 41/56] ipv4: fix buffer overflow in ip_options_compile()

Greg Kroah-Hartman
2014-07-26T19:03:08Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 10ec9472f05b45c94db3c854d22581a20b97db41 ]

There is a benign buffer overflow in ip_options_compile spotted by
AddressSanitizer[1] :

Its benign because we always can access one extra byte in skb->head
(because header is followed by struct skb_shared_info), and in this case
this byte is not even used.

[28504.910798] ==================================================================
[28504.912046] AddressSanitizer: heap-buffer-overflow in ip_options_compile
[28504.913170] Read of size 1 by thread T15843:
[28504.914026] [<ffffffff81802f91>] ip_options_compile+0x121/0x9c0
[28504.915394] [<ffffffff81804a0d>] ip_options_get_from_user+0xad/0x120
[28504.916843] [<ffffffff8180dedf>] do_ip_setsockopt.isra.15+0x8df/0x1630
[28504.918175] [<ffffffff8180ec60>] ip_setsockopt+0x30/0xa0
[28504.919490] [<ffffffff8181e59b>] tcp_setsockopt+0x5b/0x90
[28504.920835] [<ffffffff8177462f>] sock_common_setsockopt+0x5f/0x70
[28504.922208] [<ffffffff817729c2>] SyS_setsockopt+0xa2/0x140
[28504.923459] [<ffffffff818cfb69>] system_call_fastpath+0x16/0x1b
[28504.924722]
[28504.925106] Allocated by thread T15843:
[28504.925815] [<ffffffff81804995>] ip_options_get_from_user+0x35/0x120
[28504.926884] [<ffffffff8180dedf>] do_ip_setsockopt.isra.15+0x8df/0x1630
[28504.927975] [<ffffffff8180ec60>] ip_setsockopt+0x30/0xa0
[28504.929175] [<ffffffff8181e59b>] tcp_setsockopt+0x5b/0x90
[28504.930400] [<ffffffff8177462f>] sock_common_setsockopt+0x5f/0x70
[28504.931677] [<ffffffff817729c2>] SyS_setsockopt+0xa2/0x140
[28504.932851] [<ffffffff818cfb69>] system_call_fastpath+0x16/0x1b
[28504.934018]
[28504.934377] The buggy address ffff880026382828 is located 0 bytes to the right
[28504.934377] of 40-byte region [ffff880026382800, ffff880026382828)
[28504.937144]
[28504.937474] Memory state around the buggy address:
[28504.938430] ffff880026382300: ........ rrrrrrrr rrrrrrrr rrrrrrrr
[28504.939884] ffff880026382400: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28504.941294] ffff880026382500: .....rrr rrrrrrrr rrrrrrrr rrrrrrrr
[28504.942504] ffff880026382600: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28504.943483] ffff880026382700: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28504.944511] >ffff880026382800: .....rrr rrrrrrrr rrrrrrrr rrrrrrrr
[28504.945573] ^
[28504.946277] ffff880026382900: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.094949] ffff880026382a00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.096114] ffff880026382b00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.097116] ffff880026382c00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.098472] ffff880026382d00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.099804] Legend:
[28505.100269] f - 8 freed bytes
[28505.100884] r - 8 redzone bytes
[28505.101649] . - 8 allocated bytes
[28505.102406] x=1..7 - x allocated bytes + (8-x) redzone bytes
[28505.103637] ==================================================================

[1] https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerForKernel

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/ip_options.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -288,6 +288,10 @@ int ip_options_compile(struct net *net,
optptr++;
continue;
}
+ if (unlikely(l < 2)) {
+ pp_ptr = optptr;
+ goto error;
+ }
optlen = optptr[1];
if (optlen<2 || optlen>l) {
pp_ptr = optptr;