diff options
| author | Eric Dumazet <edumazet@google.com> | 2017-10-21 12:26:23 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-10-22 03:22:24 +0100 |
| commit | 864e2a1f8aac05effac6063ce316b480facb46ff (patch) | |
| tree | 8c42a0097912dbb1e841154a013c2c56f49214f3 /net/ipv6 | |
| parent | 66bdede495c71da9c5ce18542976fae53642880b (diff) | |
ipv6: flowlabel: do not leave opt->tot_len with garbage
When syzkaller team brought us a C repro for the crash [1] that
had been reported many times in the past, I finally could find
the root cause.
If FlowLabel info is merged by fl6_merge_options(), we leave
part of the opt_space storage provided by udp/raw/l2tp with random value
in opt_space.tot_len, unless a control message was provided at sendmsg()
time.
Then ip6_setup_cork() would use this random value to perform a kzalloc()
call. Undefined behavior and crashes.
Fix is to properly set tot_len in fl6_merge_options()
At the same time, we can also avoid consuming memory and cpu cycles
to clear it, if every option is copied via a kmemdup(). This is the
change in ip6_setup_cork().
[1]
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
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 6613 Comm: syz-executor0 Not tainted 4.14.0-rc4+ #127
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801cb64a100 task.stack: ffff8801cc350000
RIP: 0010:ip6_setup_cork+0x274/0x15c0 net/ipv6/ip6_output.c:1168
RSP: 0018:ffff8801cc357550 EFLAGS: 00010203
RAX: dffffc0000000000 RBX: ffff8801cc357748 RCX: 0000000000000010
RDX: 0000000000000002 RSI: ffffffff842bd1d9 RDI: 0000000000000014
RBP: ffff8801cc357620 R08: ffff8801cb17f380 R09: ffff8801cc357b10
R10: ffff8801cb64a100 R11: 0000000000000000 R12: ffff8801cc357ab0
R13: ffff8801cc357b10 R14: 0000000000000000 R15: ffff8801c3bbf0c0
FS: 00007f9c5c459700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020324000 CR3: 00000001d1cf2000 CR4: 00000000001406f0
DR0: 0000000020001010 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
ip6_make_skb+0x282/0x530 net/ipv6/ip6_output.c:1729
udpv6_sendmsg+0x2769/0x3380 net/ipv6/udp.c:1340
inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:762
sock_sendmsg_nosec net/socket.c:633 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:643
SYSC_sendto+0x358/0x5a0 net/socket.c:1750
SyS_sendto+0x40/0x50 net/socket.c:1718
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x4520a9
RSP: 002b:00007f9c5c458c08 EFLAGS: 00000216 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 00000000004520a9
RDX: 0000000000000001 RSI: 0000000020fd1000 RDI: 0000000000000016
RBP: 0000000000000086 R08: 0000000020e0afe4 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004bb1ee
R13: 00000000ffffffff R14: 0000000000000016 R15: 0000000000000029
Code: e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 ea 0f 00 00 48 8d 79 04 48 b8 00 00 00 00 00 fc ff df 45 8b 74 24 04 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RIP: ip6_setup_cork+0x274/0x15c0 net/ipv6/ip6_output.c:1168 RSP: ffff8801cc357550
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6')
| -rw-r--r-- | net/ipv6/ip6_flowlabel.c | 1 | ||||
| -rw-r--r-- | net/ipv6/ip6_output.c | 4 |
2 files changed, 3 insertions, 2 deletions
diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c index 8081bafe441b..15535ee327c5 100644 --- a/net/ipv6/ip6_flowlabel.c +++ b/net/ipv6/ip6_flowlabel.c @@ -315,6 +315,7 @@ struct ipv6_txoptions *fl6_merge_options(struct ipv6_txoptions *opt_space, } opt_space->dst1opt = fopt->dst1opt; opt_space->opt_flen = fopt->opt_flen; + opt_space->tot_len = fopt->tot_len; return opt_space; } EXPORT_SYMBOL_GPL(fl6_merge_options); diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 43ca864327c7..5110a418cc4d 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1161,11 +1161,11 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, if (WARN_ON(v6_cork->opt)) return -EINVAL; - v6_cork->opt = kzalloc(opt->tot_len, sk->sk_allocation); + v6_cork->opt = kzalloc(sizeof(*opt), sk->sk_allocation); if (unlikely(!v6_cork->opt)) return -ENOBUFS; - v6_cork->opt->tot_len = opt->tot_len; + v6_cork->opt->tot_len = sizeof(*opt); v6_cork->opt->opt_flen = opt->opt_flen; v6_cork->opt->opt_nflen = opt->opt_nflen; |