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Date: Sun, 3 Jun 2018 06:35:46 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
David Ahern <dsa@...ulusnetworks.com>
Subject: [PATCH net] net: ipv6: prevent use after free in ip6_route_mpath_notify()
syzbot reported a use-after-free [1]
Issue here is that rt_last might have been freed already.
We need to grab a refcount on it to prevent this.
[1]
BUG: KASAN: use-after-free in ip6_route_mpath_notify+0xe9/0x100 net/ipv6/route.c:4180
Read of size 4 at addr ffff8801bf789cf0 by task syz-executor756/4555
CPU: 1 PID: 4555 Comm: syz-executor756 Not tainted 4.17.0-rc7+ #78
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+0x1b9/0x294 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
ip6_route_mpath_notify+0xe9/0x100 net/ipv6/route.c:4180
ip6_route_multipath_add+0x615/0x1910 net/ipv6/route.c:4303
inet6_rtm_newroute+0xe3/0x160 net/ipv6/route.c:4391
rtnetlink_rcv_msg+0x466/0xc10 net/core/rtnetlink.c:4646
netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4664
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0x58b/0x740 net/netlink/af_netlink.c:1336
netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:629 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:639
___sys_sendmsg+0x805/0x940 net/socket.c:2117
__sys_sendmsg+0x115/0x270 net/socket.c:2155
__do_sys_sendmsg net/socket.c:2164 [inline]
__se_sys_sendmsg net/socket.c:2162 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441819
RSP: 002b:00007ffe841e19d8 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441819
RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000004
RBP: 00000000006cd018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000402510
R13: 00000000004025a0 R14: 0000000000000000 R15: 0000000000000000
Allocated by task 4555:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
dst_alloc+0xbb/0x1d0 net/core/dst.c:104
__ip6_dst_alloc+0x35/0xa0 net/ipv6/route.c:361
ip6_dst_alloc+0x29/0xb0 net/ipv6/route.c:376
ip6_route_info_create+0x4d4/0x3a30 net/ipv6/route.c:2834
ip6_route_multipath_add+0xc7e/0x1910 net/ipv6/route.c:4240
inet6_rtm_newroute+0xe3/0x160 net/ipv6/route.c:4391
rtnetlink_rcv_msg+0x466/0xc10 net/core/rtnetlink.c:4646
netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4664
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0x58b/0x740 net/netlink/af_netlink.c:1336
netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:629 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:639
___sys_sendmsg+0x805/0x940 net/socket.c:2117
__sys_sendmsg+0x115/0x270 net/socket.c:2155
__do_sys_sendmsg net/socket.c:2164 [inline]
__se_sys_sendmsg net/socket.c:2162 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 4555:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
dst_destroy+0x267/0x3c0 net/core/dst.c:140
dst_release_immediate+0x71/0x9e net/core/dst.c:205
fib6_add+0xa40/0x1650 net/ipv6/ip6_fib.c:1305
__ip6_ins_rt+0x6c/0x90 net/ipv6/route.c:1011
ip6_route_multipath_add+0x513/0x1910 net/ipv6/route.c:4267
inet6_rtm_newroute+0xe3/0x160 net/ipv6/route.c:4391
rtnetlink_rcv_msg+0x466/0xc10 net/core/rtnetlink.c:4646
netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4664
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0x58b/0x740 net/netlink/af_netlink.c:1336
netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:629 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:639
___sys_sendmsg+0x805/0x940 net/socket.c:2117
__sys_sendmsg+0x115/0x270 net/socket.c:2155
__do_sys_sendmsg net/socket.c:2164 [inline]
__se_sys_sendmsg net/socket.c:2162 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
The buggy address belongs to the object at ffff8801bf789c40
which belongs to the cache ip6_dst_cache of size 320
The buggy address is located 176 bytes inside of
320-byte region [ffff8801bf789c40, ffff8801bf789d80)
The buggy address belongs to the page:
page:ffffea0006fde240 count:1 mapcount:0 mapping:ffff8801bf789040 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bf789040 0000000000000000 000000010000000a
raw: ffffea0006f92f20 ffff8801cd9e7248 ffff8801cda00c40 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8801bf789b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801bf789c00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff8801bf789c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801bf789d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801bf789d80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
Fixes: 3b1137fe7482 ("net: ipv6: Change notifications for multipath add to RTA_MULTIPATH")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: David Ahern <dsa@...ulusnetworks.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
---
net/ipv6/route.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f4d61736c41abe8cd7f439c4a37100e90c1eacca..830eefdbdb6734eb81ea0322fb6077ee20be1889 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -4263,7 +4263,9 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
err_nh = NULL;
list_for_each_entry(nh, &rt6_nh_list, next) {
+ dst_release(&rt_last->dst);
rt_last = nh->rt6_info;
+ dst_hold(&rt_last->dst);
err = __ip6_ins_rt(nh->rt6_info, info, &nh->mxc, extack);
/* save reference to first route for notification */
if (!rt_notif && !err)
@@ -4317,7 +4319,7 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
list_del(&nh->next);
kfree(nh);
}
-
+ dst_release(&rt_last->dst);
return err;
}
--
2.17.1.1185.g55be947832-goog
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