[PATCH 3.16 118/366] net: metrics: add proper netlink validation

Ben Hutchings
2018-11-12T05:57:38Z

From: Eric Dumazet <edumazet@google.com>

commit 5b5e7a0de2bbf2a1afcd9f49e940010e9fb80d53 upstream.

Before using nla_get_u32(), better make sure the attribute
is of the proper size.

Code recently was changed, but bug has been there from beginning
of git.

BUG: KMSAN: uninit-value in rtnetlink_put_metrics+0x553/0x960 net/core/rtnetlink.c:746
CPU: 1 PID: 14139 Comm: syz-executor6 Not tainted 4.17.0-rc5+ #103
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x185/0x1d0 lib/dump_stack.c:113
kmsan_report+0x149/0x260 mm/kmsan/kmsan.c:1084
__msan_warning_32+0x6e/0xc0 mm/kmsan/kmsan_instr.c:686
rtnetlink_put_metrics+0x553/0x960 net/core/rtnetlink.c:746
fib_dump_info+0xc42/0x2190 net/ipv4/fib_semantics.c:1361
rtmsg_fib+0x65f/0x8c0 net/ipv4/fib_semantics.c:419
fib_table_insert+0x2314/0x2b50 net/ipv4/fib_trie.c:1287
inet_rtm_newroute+0x210/0x340 net/ipv4/fib_frontend.c:779
rtnetlink_rcv_msg+0xa32/0x1560 net/core/rtnetlink.c:4646
netlink_rcv_skb+0x378/0x600 net/netlink/af_netlink.c:2448
rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:4664
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0x1678/0x1750 net/netlink/af_netlink.c:1336
netlink_sendmsg+0x104f/0x1350 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:629 [inline]
sock_sendmsg net/socket.c:639 [inline]
___sys_sendmsg+0xec0/0x1310 net/socket.c:2117
__sys_sendmsg net/socket.c:2155 [inline]
__do_sys_sendmsg net/socket.c:2164 [inline]
__se_sys_sendmsg net/socket.c:2162 [inline]
__x64_sys_sendmsg+0x331/0x460 net/socket.c:2162
do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x455a09
RSP: 002b:00007faae5fd8c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007faae5fd96d4 RCX: 0000000000455a09
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000005d0 R14: 00000000006fdc20 R15: 0000000000000000

Uninit was stored to memory at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
kmsan_save_stack mm/kmsan/kmsan.c:294 [inline]
kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:685
__msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:529
fib_convert_metrics net/ipv4/fib_semantics.c:1056 [inline]
fib_create_info+0x2d46/0x9dc0 net/ipv4/fib_semantics.c:1150
fib_table_insert+0x3e4/0x2b50 net/ipv4/fib_trie.c:1146
inet_rtm_newroute+0x210/0x340 net/ipv4/fib_frontend.c:779
rtnetlink_rcv_msg+0xa32/0x1560 net/core/rtnetlink.c:4646
netlink_rcv_skb+0x378/0x600 net/netlink/af_netlink.c:2448
rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:4664
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0x1678/0x1750 net/netlink/af_netlink.c:1336
netlink_sendmsg+0x104f/0x1350 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:629 [inline]
sock_sendmsg net/socket.c:639 [inline]
___sys_sendmsg+0xec0/0x1310 net/socket.c:2117
__sys_sendmsg net/socket.c:2155 [inline]
__do_sys_sendmsg net/socket.c:2164 [inline]
__se_sys_sendmsg net/socket.c:2162 [inline]
__x64_sys_sendmsg+0x331/0x460 net/socket.c:2162
do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:189
kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:315
kmsan_slab_alloc+0x10/0x20 mm/kmsan/kmsan.c:322
slab_post_alloc_hook mm/slab.h:446 [inline]
slab_alloc_node mm/slub.c:2753 [inline]
__kmalloc_node_track_caller+0xb32/0x11b0 mm/slub.c:4395
__kmalloc_reserve net/core/skbuff.c:138 [inline]
__alloc_skb+0x2cb/0x9e0 net/core/skbuff.c:206
alloc_skb include/linux/skbuff.h:988 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
netlink_sendmsg+0x76e/0x1350 net/netlink/af_netlink.c:1876
sock_sendmsg_nosec net/socket.c:629 [inline]
sock_sendmsg net/socket.c:639 [inline]
___sys_sendmsg+0xec0/0x1310 net/socket.c:2117
__sys_sendmsg net/socket.c:2155 [inline]
__do_sys_sendmsg net/socket.c:2164 [inline]
__se_sys_sendmsg net/socket.c:2162 [inline]
__x64_sys_sendmsg+0x331/0x460 net/socket.c:2162
do_syscall_64+0x152/0x230 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: a919525ad832 ("net: Move fib_convert_metrics to metrics file")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: Metrics are parsed in fib_create_info()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -862,6 +862,8 @@ struct fib_info *fib_create_info(struct

if (type > RTAX_MAX)
goto err_inval;
+ if (nla_len(nla) != sizeof(u32))
+ goto err_inval;
val = nla_get_u32(nla);
if (type == RTAX_ADVMSS && val > 65535 - 40)
val = 65535 - 40;