From bc3aae2bbac46dd894c89db5d5e98f7f0ef9e205 Mon Sep 17 00:00:00 2001 From: Roopa Prabhu Date: Wed, 16 Aug 2017 12:38:52 -0700 Subject: [PATCH] net: check and errout if res->fi is NULL when RTM_F_FIB_MATCH is set Syzkaller hit 'general protection fault in fib_dump_info' bug on commit 4.13-rc5.. Guilty file: net/ipv4/fib_semantics.c kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] SMP KASAN Modules linked in: CPU: 0 PID: 2808 Comm: syz-executor0 Not tainted 4.13.0-rc5 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 task: ffff880078562700 task.stack: ffff880078110000 RIP: 0010:fib_dump_info+0x388/0x1170 net/ipv4/fib_semantics.c:1314 RSP: 0018:ffff880078117010 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: 00000000000000fe RCX: 0000000000000002 RDX: 0000000000000006 RSI: ffff880078117084 RDI: 0000000000000030 RBP: ffff880078117268 R08: 000000000000000c R09: ffff8800780d80c8 R10: 0000000058d629b4 R11: 0000000067fce681 R12: 0000000000000000 R13: ffff8800784bd540 R14: ffff8800780d80b5 R15: ffff8800780d80a4 FS: 00000000022fa940(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004387d0 CR3: 0000000079135000 CR4: 00000000000006f0 Call Trace: inet_rtm_getroute+0xc89/0x1f50 net/ipv4/route.c:2766 rtnetlink_rcv_msg+0x288/0x680 net/core/rtnetlink.c:4217 netlink_rcv_skb+0x340/0x470 net/netlink/af_netlink.c:2397 rtnetlink_rcv+0x28/0x30 net/core/rtnetlink.c:4223 netlink_unicast_kernel net/netlink/af_netlink.c:1265 [inline] netlink_unicast+0x4c4/0x6e0 net/netlink/af_netlink.c:1291 netlink_sendmsg+0x8c4/0xca0 net/netlink/af_netlink.c:1854 sock_sendmsg_nosec net/socket.c:633 [inline] sock_sendmsg+0xca/0x110 net/socket.c:643 ___sys_sendmsg+0x779/0x8d0 net/socket.c:2035 __sys_sendmsg+0xd1/0x170 net/socket.c:2069 SYSC_sendmsg net/socket.c:2080 [inline] SyS_sendmsg+0x2d/0x50 net/socket.c:2076 entry_SYSCALL_64_fastpath+0x1a/0xa5 RIP: 0033:0x4512e9 RSP: 002b:00007ffc75584cc8 EFLAGS: 00000216 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00000000004512e9 RDX: 0000000000000000 RSI: 0000000020f2cfc8 RDI: 0000000000000003 RBP: 000000000000000e R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000216 R12: fffffffffffffffe R13: 0000000000718000 R14: 0000000020c44ff0 R15: 0000000000000000 Code: 00 0f b6 8d ec fd ff ff 48 8b 85 f0 fd ff ff 88 48 17 48 8b 45 28 48 8d 78 30 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e cb 0c 00 00 48 8b 45 28 44 RIP: fib_dump_info+0x388/0x1170 net/ipv4/fib_semantics.c:1314 RSP: ffff880078117010 ---[ end trace 254a7af28348f88b ]--- This patch adds a res->fi NULL check. example run: $ip route get 0.0.0.0 iif virt1-0 broadcast 0.0.0.0 dev lo cache iif virt1-0 $ip route get 0.0.0.0 iif virt1-0 fibmatch RTNETLINK answers: No route to host Reported-by: idaifish Reported-by: Dmitry Vyukov Fixes: b61798130f1b ("net: ipv4: RTM_GETROUTE: return matched fib result when requested") Signed-off-by: Roopa Prabhu Signed-off-by: David S. Miller --- net/ipv4/route.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index fe877a4a72b1..2331de20ca50 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2763,14 +2763,21 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh, if (rtm->rtm_flags & RTM_F_LOOKUP_TABLE) table_id = rt->rt_table_id; - if (rtm->rtm_flags & RTM_F_FIB_MATCH) + if (rtm->rtm_flags & RTM_F_FIB_MATCH) { + if (!res.fi) { + err = fib_props[res.type].error; + if (!err) + err = -EHOSTUNREACH; + goto errout_free; + } err = fib_dump_info(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq, RTM_NEWROUTE, table_id, rt->rt_type, res.prefix, res.prefixlen, fl4.flowi4_tos, res.fi, 0); - else + } else { err = rt_fill_info(net, dst, src, table_id, &fl4, skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq); + } if (err < 0) goto errout_free; -- 2.20.1