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Date: Mon, 9 Apr 2018 06:43:27 -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>
Subject: [PATCH net] inetpeer: fix uninit-value in inet_getpeer
syzbot/KMSAN reported that p->dtime was read while it was
not yet initialized in :
delta = (__u32)jiffies - p->dtime;
if (delta < ttl || !refcount_dec_if_one(&p->refcnt))
gc_stack[i] = NULL;
This is a false positive, because the inetpeer wont be erased
from rb-tree if the refcount_dec_if_one(&p->refcnt) does not
succeed. And this wont happen before first inet_putpeer() call
for this inetpeer has been done, and ->dtime field is written
exactly before the refcount_dec_and_test(&p->refcnt).
The KMSAN report was :
BUG: KMSAN: uninit-value in inet_peer_gc net/ipv4/inetpeer.c:163 [inline]
BUG: KMSAN: uninit-value in inet_getpeer+0x1567/0x1e70 net/ipv4/inetpeer.c:228
CPU: 0 PID: 9494 Comm: syz-executor5 Not tainted 4.16.0+ #82
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+0x185/0x1d0 lib/dump_stack.c:53
kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
__msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
inet_peer_gc net/ipv4/inetpeer.c:163 [inline]
inet_getpeer+0x1567/0x1e70 net/ipv4/inetpeer.c:228
inet_getpeer_v4 include/net/inetpeer.h:110 [inline]
icmpv4_xrlim_allow net/ipv4/icmp.c:330 [inline]
icmp_send+0x2b44/0x3050 net/ipv4/icmp.c:725
ip_options_compile+0x237c/0x29f0 net/ipv4/ip_options.c:472
ip_rcv_options net/ipv4/ip_input.c:284 [inline]
ip_rcv_finish+0xda8/0x16d0 net/ipv4/ip_input.c:365
NF_HOOK include/linux/netfilter.h:288 [inline]
ip_rcv+0x119d/0x16f0 net/ipv4/ip_input.c:493
__netif_receive_skb_core+0x47cf/0x4a80 net/core/dev.c:4562
__netif_receive_skb net/core/dev.c:4627 [inline]
netif_receive_skb_internal+0x49d/0x630 net/core/dev.c:4701
netif_receive_skb+0x230/0x240 net/core/dev.c:4725
tun_rx_batched drivers/net/tun.c:1555 [inline]
tun_get_user+0x6d88/0x7580 drivers/net/tun.c:1962
tun_chr_write_iter+0x1d4/0x330 drivers/net/tun.c:1990
do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
do_iter_write+0x30d/0xd40 fs/read_write.c:932
vfs_writev fs/read_write.c:977 [inline]
do_writev+0x3c9/0x830 fs/read_write.c:1012
SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
SyS_writev+0x56/0x80 fs/read_write.c:1082
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x455111
RSP: 002b:00007fae0365cba0 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 000000000000002e RCX: 0000000000455111
RDX: 0000000000000001 RSI: 00007fae0365cbf0 RDI: 00000000000000fc
RBP: 0000000020000040 R08: 00000000000000fc R09: 0000000000000000
R10: 000000000000002e R11: 0000000000000293 R12: 00000000ffffffff
R13: 0000000000000658 R14: 00000000006fc8e0 R15: 0000000000000000
Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
kmem_cache_alloc+0xaab/0xb90 mm/slub.c:2756
inet_getpeer+0xed8/0x1e70 net/ipv4/inetpeer.c:210
inet_getpeer_v4 include/net/inetpeer.h:110 [inline]
ip4_frag_init+0x4d1/0x740 net/ipv4/ip_fragment.c:153
inet_frag_alloc net/ipv4/inet_fragment.c:369 [inline]
inet_frag_create net/ipv4/inet_fragment.c:385 [inline]
inet_frag_find+0x7da/0x1610 net/ipv4/inet_fragment.c:418
ip_find net/ipv4/ip_fragment.c:275 [inline]
ip_defrag+0x448/0x67a0 net/ipv4/ip_fragment.c:676
ip_check_defrag+0x775/0xda0 net/ipv4/ip_fragment.c:724
packet_rcv_fanout+0x2a8/0x8d0 net/packet/af_packet.c:1447
deliver_skb net/core/dev.c:1897 [inline]
deliver_ptype_list_skb net/core/dev.c:1912 [inline]
__netif_receive_skb_core+0x314a/0x4a80 net/core/dev.c:4545
__netif_receive_skb net/core/dev.c:4627 [inline]
netif_receive_skb_internal+0x49d/0x630 net/core/dev.c:4701
netif_receive_skb+0x230/0x240 net/core/dev.c:4725
tun_rx_batched drivers/net/tun.c:1555 [inline]
tun_get_user+0x6d88/0x7580 drivers/net/tun.c:1962
tun_chr_write_iter+0x1d4/0x330 drivers/net/tun.c:1990
do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
do_iter_write+0x30d/0xd40 fs/read_write.c:932
vfs_writev fs/read_write.c:977 [inline]
do_writev+0x3c9/0x830 fs/read_write.c:1012
SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
SyS_writev+0x56/0x80 fs/read_write.c:1082
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
---
net/ipv4/inetpeer.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 1f04bd91fc2e999ddb82f4be92d39d229166b691..d757b9642d0d1c418bffad5bcd50e8e7bf336c66 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -211,6 +211,7 @@ struct inet_peer *inet_getpeer(struct inet_peer_base *base,
p = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
if (p) {
p->daddr = *daddr;
+ p->dtime = (__u32)jiffies;
refcount_set(&p->refcnt, 2);
atomic_set(&p->rid, 0);
p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
--
2.17.0.484.g0c8726318c-goog
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