From 348a4002729ccab8b888b38cbc099efa2f2a2036 Mon Sep 17 00:00:00 2001 From: Wei Wang Date: Fri, 18 Aug 2017 17:14:49 -0700 Subject: ipv6: repair fib6 tree in failure case In fib6_add(), it is possible that fib6_add_1() picks an intermediate node and sets the node's fn->leaf to NULL in order to add this new route. However, if fib6_add_rt2node() fails to add the new route for some reason, fn->leaf will be left as NULL and could potentially cause crash when fn->leaf is accessed in fib6_locate(). This patch makes sure fib6_repair_tree() is called to properly repair fn->leaf in the above failure case. Here is the syzkaller reported general protection fault in fib6_locate: kasan: CONFIG_KASAN_INLINE enabled 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: 40937 Comm: syz-executor3 Not tainted Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801d7d64100 ti: ffff8801d01a0000 task.ti: ffff8801d01a0000 RIP: 0010:[] [] __ipv6_prefix_equal64_half include/net/ipv6.h:475 [inline] RIP: 0010:[] [] ipv6_prefix_equal include/net/ipv6.h:492 [inline] RIP: 0010:[] [] fib6_locate_1 net/ipv6/ip6_fib.c:1210 [inline] RIP: 0010:[] [] fib6_locate+0x281/0x3c0 net/ipv6/ip6_fib.c:1233 RSP: 0018:ffff8801d01a36a8 EFLAGS: 00010202 RAX: 0000000000000020 RBX: ffff8801bc790e00 RCX: ffffc90002983000 RDX: 0000000000001219 RSI: ffff8801d01a37a0 RDI: 0000000000000100 RBP: ffff8801d01a36f0 R08: 00000000000000ff R09: 0000000000000000 R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000000001 R13: dffffc0000000000 R14: ffff8801d01a37a0 R15: 0000000000000000 FS: 00007f6afd68c700(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004c6340 CR3: 00000000ba41f000 CR4: 00000000001426f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffff8801d01a37a8 ffff8801d01a3780 ffffed003a0346f5 0000000c82a23ea0 ffff8800b7bd7700 ffff8801d01a3780 ffff8800b6a1c940 ffffffff82a23ea0 ffff8801d01a3920 ffff8801d01a3748 ffffffff82a223d6 ffff8801d7d64988 Call Trace: [] ip6_route_del+0x106/0x570 net/ipv6/route.c:2109 [] inet6_rtm_delroute+0xfd/0x100 net/ipv6/route.c:3075 [] rtnetlink_rcv_msg+0x549/0x7a0 net/core/rtnetlink.c:3450 [] netlink_rcv_skb+0x141/0x370 net/netlink/af_netlink.c:2281 [] rtnetlink_rcv+0x2f/0x40 net/core/rtnetlink.c:3456 [] netlink_unicast_kernel net/netlink/af_netlink.c:1206 [inline] [] netlink_unicast+0x518/0x750 net/netlink/af_netlink.c:1232 [] netlink_sendmsg+0x8ce/0xc30 net/netlink/af_netlink.c:1778 [] sock_sendmsg_nosec net/socket.c:609 [inline] [] sock_sendmsg+0xcf/0x110 net/socket.c:619 [] sock_write_iter+0x222/0x3a0 net/socket.c:834 [] new_sync_write+0x1dd/0x2b0 fs/read_write.c:478 [] __vfs_write+0xe4/0x110 fs/read_write.c:491 [] vfs_write+0x178/0x4b0 fs/read_write.c:538 [] SYSC_write fs/read_write.c:585 [inline] [] SyS_write+0xd9/0x1b0 fs/read_write.c:577 [] entry_SYSCALL_64_fastpath+0x12/0x17 Note: there is no "Fixes" tag as this seems to be a bug introduced very early. Signed-off-by: Wei Wang Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv6/ip6_fib.c | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) (limited to 'net/ipv6/ip6_fib.c') diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index e6f878067c68..5cc0ea038198 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -1018,7 +1018,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, /* Create subtree root node */ sfn = node_alloc(); if (!sfn) - goto st_failure; + goto failure; sfn->leaf = info->nl_net->ipv6.ip6_null_entry; atomic_inc(&info->nl_net->ipv6.ip6_null_entry->rt6i_ref); @@ -1035,12 +1035,12 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, if (IS_ERR(sn)) { /* If it is failed, discard just allocated - root, and then (in st_failure) stale node + root, and then (in failure) stale node in main tree. */ node_free(sfn); err = PTR_ERR(sn); - goto st_failure; + goto failure; } /* Now link new subtree to main tree */ @@ -1055,7 +1055,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, if (IS_ERR(sn)) { err = PTR_ERR(sn); - goto st_failure; + goto failure; } } @@ -1096,18 +1096,17 @@ out: atomic_inc(&pn->leaf->rt6i_ref); } #endif - /* Always release dst as dst->__refcnt is guaranteed - * to be taken before entering this function - */ - dst_release_immediate(&rt->dst); + goto failure; } return err; -#ifdef CONFIG_IPV6_SUBTREES - /* Subtree creation failed, probably main tree node - is orphan. If it is, shoot it. +failure: + /* fn->leaf could be NULL if fn is an intermediate node and we + * failed to add the new route to it in both subtree creation + * failure and fib6_add_rt2node() failure case. + * In both cases, fib6_repair_tree() should be called to fix + * fn->leaf. */ -st_failure: if (fn && !(fn->fn_flags & (RTN_RTINFO|RTN_ROOT))) fib6_repair_tree(info->nl_net, fn); /* Always release dst as dst->__refcnt is guaranteed @@ -1115,7 +1114,6 @@ st_failure: */ dst_release_immediate(&rt->dst); return err; -#endif } /* -- cgit v1.2.3-59-g8ed1b