From 223105654ef9efb8c040cfb91e03ce1a8de69dd0 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 21 Jul 2014 07:17:42 +0200 Subject: [PATCH] ipv4: fix buffer overflow in ip_options_compile() [ 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] [] ip_options_compile+0x121/0x9c0 [28504.915394] [] ip_options_get_from_user+0xad/0x120 [28504.916843] [] do_ip_setsockopt.isra.15+0x8df/0x1630 [28504.918175] [] ip_setsockopt+0x30/0xa0 [28504.919490] [] tcp_setsockopt+0x5b/0x90 [28504.920835] [] sock_common_setsockopt+0x5f/0x70 [28504.922208] [] SyS_setsockopt+0xa2/0x140 [28504.923459] [] system_call_fastpath+0x16/0x1b [28504.924722] [28504.925106] Allocated by thread T15843: [28504.925815] [] ip_options_get_from_user+0x35/0x120 [28504.926884] [] do_ip_setsockopt.isra.15+0x8df/0x1630 [28504.927975] [] ip_setsockopt+0x30/0xa0 [28504.929175] [] tcp_setsockopt+0x5b/0x90 [28504.930400] [] sock_common_setsockopt+0x5f/0x70 [28504.931677] [] SyS_setsockopt+0xa2/0x140 [28504.932851] [] 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 Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/ipv4/ip_options.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c index 40eb4fc27913..08623e2c4e5d 100644 --- a/net/ipv4/ip_options.c +++ b/net/ipv4/ip_options.c @@ -277,6 +277,10 @@ 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; -- 2.39.2