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Message-Id: <20180118184003.82818-1-tracywwnj@gmail.com>
Date: Thu, 18 Jan 2018 10:40:03 -0800
From: Wei Wang <weiwan@...gle.com>
To: David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Cc: Eric Dumazet <edumazet@...gle.com>,
Martin KaFai Lau <kafai@...com>, Wei Wang <weiwan@...gle.com>
Subject: [PATCH net] ipv6: don't let tb6_root node share routes with other node
From: Wei Wang <weiwan@...gle.com>
After commit 4512c43eac7e, if we add a route to the subtree of tb6_root
which does not have any route attached to it yet, the current code will
let tb6_root and the node in the subtree share the same route.
This could cause problem cause tb6_root has RTN_INFO flag marked and the
tree repair and clean up code will not work properly.
This commit makes sure tb6_root->leaf points back to null_entry instead
of sharing route with other node.
It fixes the following syzkaller reported issue:
BUG: KASAN: use-after-free in ipv6_prefix_equal include/net/ipv6.h:540 [inline]
BUG: KASAN: use-after-free in fib6_add_1+0x165f/0x1790 net/ipv6/ip6_fib.c:618
Read of size 8 at addr ffff8801bc043498 by task syz-executor5/19819
CPU: 1 PID: 19819 Comm: syz-executor5 Not tainted 4.15.0-rc7+ #186
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x25b/0x340 mm/kasan/report.c:409
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
ipv6_prefix_equal include/net/ipv6.h:540 [inline]
fib6_add_1+0x165f/0x1790 net/ipv6/ip6_fib.c:618
fib6_add+0x5fa/0x1540 net/ipv6/ip6_fib.c:1214
__ip6_ins_rt+0x6c/0x90 net/ipv6/route.c:1003
ip6_route_add+0x141/0x190 net/ipv6/route.c:2790
ipv6_route_ioctl+0x4db/0x6b0 net/ipv6/route.c:3299
inet6_ioctl+0xef/0x1e0 net/ipv6/af_inet6.c:520
sock_do_ioctl+0x65/0xb0 net/socket.c:958
sock_ioctl+0x2c2/0x440 net/socket.c:1055
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x452ac9
RSP: 002b:00007fd42b321c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9
RDX: 0000000020fd7000 RSI: 000000000000890b RDI: 0000000000000013
RBP: 000000000000049e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f4f70
R13: 00000000ffffffff R14: 00007fd42b3226d4 R15: 0000000000000000
Fixes: 4512c43eac7e ("ipv6: remove null_entry before adding default route")
Signed-off-by: Wei Wang <weiwan@...gle.com>
Acked-by: Eric Dumazet <edumazet@...gle.com>
---
net/ipv6/ip6_fib.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 9dcc3924a975..217683d40f12 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1226,8 +1226,14 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
}
if (!rcu_access_pointer(fn->leaf)) {
- atomic_inc(&rt->rt6i_ref);
- rcu_assign_pointer(fn->leaf, rt);
+ if (fn->fn_flags & RTN_TL_ROOT) {
+ /* put back null_entry for root node */
+ rcu_assign_pointer(fn->leaf,
+ info->nl_net->ipv6.ip6_null_entry);
+ } else {
+ atomic_inc(&rt->rt6i_ref);
+ rcu_assign_pointer(fn->leaf, rt);
+ }
}
fn = sn;
}
--
2.16.0.rc1.238.g530d649a79-goog
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