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Date: Thu, 19 Apr 2018 09:14:53 -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-next] net/ipv6: Fix ip6_convert_metrics() bug
If ip6_convert_metrics() fails to allocate memory, it should not
overwrite rt->fib6_metrics or we risk a crash later as syzbot found.
BUG: KASAN: null-ptr-deref in atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
BUG: KASAN: null-ptr-deref in refcount_sub_and_test+0x92/0x330 lib/refcount.c:179
Read of size 4 at addr 0000000000000044 by task syzkaller832429/4487
CPU: 1 PID: 4487 Comm: syzkaller832429 Not tainted 4.16.0+ #6
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
kasan_report_error mm/kasan/report.c:352 [inline]
kasan_report.cold.7+0x6d/0x2fe mm/kasan/report.c:412
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
refcount_sub_and_test+0x92/0x330 lib/refcount.c:179
refcount_dec_and_test+0x1a/0x20 lib/refcount.c:212
fib6_info_destroy+0x2d0/0x3c0 net/ipv6/ip6_fib.c:206
fib6_info_release include/net/ip6_fib.h:304 [inline]
ip6_route_info_create+0x677/0x3240 net/ipv6/route.c:3020
ip6_route_add+0x23/0xb0 net/ipv6/route.c:3030
inet6_rtm_newroute+0x142/0x160 net/ipv6/route.c:4406
rtnetlink_rcv_msg+0x466/0xc10 net/core/rtnetlink.c:4648
netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4666
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
SYSC_sendmsg net/socket.c:2164 [inline]
SyS_sendmsg+0x29/0x30 net/socket.c:2162
do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
Fixes: d4ead6b34b67 ("net/ipv6: move metrics from dst to rt6_info")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: David Ahern <dsa@...ulusnetworks.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
---
net/ipv6/route.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f9c363327d620322dda2269d8398a5dc5de7aa4e..9279f4ec84b6b885357390d3de0826a8a4c54daf 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2600,21 +2600,19 @@ static int ip6_dst_gc(struct dst_ops *ops)
static int ip6_convert_metrics(struct net *net, struct fib6_info *rt,
struct fib6_config *cfg)
{
- int err = 0;
+ struct dst_metrics *p;
- if (cfg->fc_mx) {
- rt->fib6_metrics = kzalloc(sizeof(*rt->fib6_metrics),
- GFP_KERNEL);
- if (unlikely(!rt->fib6_metrics))
- return -ENOMEM;
+ if (!cfg->fc_mx)
+ return 0;
- refcount_set(&rt->fib6_metrics->refcnt, 1);
+ p = kzalloc(sizeof(*rt->fib6_metrics), GFP_KERNEL);
+ if (unlikely(!p))
+ return -ENOMEM;
- err = ip_metrics_convert(net, cfg->fc_mx, cfg->fc_mx_len,
- rt->fib6_metrics->metrics);
- }
+ refcount_set(&p->refcnt, 1);
+ rt->fib6_metrics = p;
- return err;
+ return ip_metrics_convert(net, cfg->fc_mx, cfg->fc_mx_len, p->metrics);
}
static struct rt6_info *ip6_nh_lookup_table(struct net *net,
--
2.17.0.484.g0c8726318c-goog
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