From 383143f31d7d3525a1dbff733d52fff917f82f15 Mon Sep 17 00:00:00 2001 From: Wei Wang Date: Wed, 16 Aug 2017 11:18:09 -0700 Subject: [PATCH] ipv6: reset fn->rr_ptr when replacing route syzcaller reported the following use-after-free issue in rt6_select(): BUG: KASAN: use-after-free in rt6_select net/ipv6/route.c:755 [inline] at addr ffff8800bc6994e8 BUG: KASAN: use-after-free in ip6_pol_route.isra.46+0x1429/0x1470 net/ipv6/route.c:1084 at addr ffff8800bc6994e8 Read of size 4 by task syz-executor1/439628 CPU: 0 PID: 439628 Comm: syz-executor1 Not tainted 4.3.5+ #8 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 ffff88018fe435b0 ffffffff81ca384d ffff8801d3588c00 ffff8800bc699380 ffff8800bc699500 dffffc0000000000 ffff8801d40a47c0 ffff88018fe435d8 ffffffff81735751 ffff88018fe43660 ffff8800bc699380 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 sctp: [Deprecated]: syz-executor0 (pid 439615) Use of struct sctp_assoc_value in delayed_ack socket option. Use struct sctp_sack_info instead [] kasan_object_err+0x21/0x70 mm/kasan/report.c:158 [] print_address_description mm/kasan/report.c:196 [inline] [] kasan_report_error+0x1b4/0x4a0 mm/kasan/report.c:285 [] kasan_report mm/kasan/report.c:305 [inline] [] __asan_report_load4_noabort+0x43/0x50 mm/kasan/report.c:325 [] rt6_select net/ipv6/route.c:755 [inline] [] ip6_pol_route.isra.46+0x1429/0x1470 net/ipv6/route.c:1084 [] ip6_pol_route_output+0x81/0xb0 net/ipv6/route.c:1203 [] fib6_rule_action+0x1f0/0x680 net/ipv6/fib6_rules.c:95 [] fib_rules_lookup+0x2a6/0x7a0 net/core/fib_rules.c:223 [] fib6_rule_lookup+0xd0/0x250 net/ipv6/fib6_rules.c:41 [] ip6_route_output+0x1d6/0x2c0 net/ipv6/route.c:1224 [] ip6_dst_lookup_tail+0x4d2/0x890 net/ipv6/ip6_output.c:943 [] ip6_dst_lookup_flow+0x9a/0x250 net/ipv6/ip6_output.c:1079 [] ip6_datagram_dst_update+0x538/0xd40 net/ipv6/datagram.c:91 [] __ip6_datagram_connect net/ipv6/datagram.c:251 [inline] [] ip6_datagram_connect+0x518/0xe50 net/ipv6/datagram.c:272 [] ip6_datagram_connect_v6_only+0x63/0x90 net/ipv6/datagram.c:284 [] inet_dgram_connect+0x170/0x1f0 net/ipv4/af_inet.c:564 [] SYSC_connect+0x1a7/0x2f0 net/socket.c:1582 [] SyS_connect+0x29/0x30 net/socket.c:1563 [] entry_SYSCALL_64_fastpath+0x12/0x17 Object at ffff8800bc699380, in cache ip6_dst_cache size: 384 The root cause of it is that in fib6_add_rt2node(), when it replaces an existing route with the new one, it does not update fn->rr_ptr. This commit resets fn->rr_ptr to NULL when it points to a route which is replaced in fib6_add_rt2node(). Fixes: 27596472473a ("ipv6: fix ECMP route replacement") Signed-off-by: Wei Wang Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv6/ip6_fib.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index ebb299cf72b7..e6f878067c68 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -914,6 +914,8 @@ add: } nsiblings = iter->rt6i_nsiblings; fib6_purge_rt(iter, fn, info->nl_net); + if (fn->rr_ptr == iter) + fn->rr_ptr = NULL; rt6_release(iter); if (nsiblings) { @@ -926,6 +928,8 @@ add: if (rt6_qualify_for_ecmp(iter)) { *ins = iter->dst.rt6_next; fib6_purge_rt(iter, fn, info->nl_net); + if (fn->rr_ptr == iter) + fn->rr_ptr = NULL; rt6_release(iter); nsiblings--; } else { -- 2.20.1