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tcp: Check daddr_cache before use in tracepoint

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Running perf in one window to capture tcp_retransmit_skb tracepoint:
    $ perf record -e tcp:tcp_retransmit_skb -a

And causing a retransmission on an active TCP session (e.g., dropping
packets in the receiver, changing MTU on the interface to 500 and back
to 1500) triggers a panic:

[   58.543144] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[   58.545300] IP: perf_trace_tcp_retransmit_skb+0xd0/0x145
[   58.546770] PGD 0 P4D 0
[   58.547472] Oops: 0000 [#1] SMP
[   58.548328] Modules linked in: vrf
[   58.549262] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-rc4+ #26
[   58.551004] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
[   58.554560] task: ffffffff81a0e540 task.stack: ffffffff81a00000
[   58.555817] RIP: 0010:perf_trace_tcp_retransmit_skb+0xd0/0x145
[   58.557137] RSP: 0018:ffff88003fc03d68 EFLAGS: 00010282
[   58.558292] RAX: 0000000000000000 RBX: ffffe8ffffc0ec80 RCX: ffff880038543098
[   58.559850] RDX: 0400000000000000 RSI: ffff88003fc03d70 RDI: ffff88003fc14b68
[   58.561099] RBP: ffff88003fc03da8 R08: 0000000000000000 R09: ffffea0000d3224a
[   58.562005] R10: ffff88003fc03db8 R11: 0000000000000010 R12: ffff8800385428c0
[   58.562930] R13: ffffe8ffffc0e478 R14: ffffffff81a93a40 R15: ffff88003d4f0c00
[   58.563845] FS:  0000000000000000(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000
[   58.564873] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   58.565613] CR2: 0000000000000008 CR3: 000000003d68f004 CR4: 00000000000606f0
[   58.566538] Call Trace:
[   58.566865]  <IRQ>
[   58.567140]  __tcp_retransmit_skb+0x4ab/0x4c6
[   58.567704]  ? tcp_set_ca_state+0x22/0x3f
[   58.568231]  tcp_retransmit_skb+0x14/0xa3
[   58.568754]  tcp_retransmit_timer+0x472/0x5e3
[   58.569324]  ? tcp_write_timer_handler+0x1e9/0x1e9
[   58.569946]  tcp_write_timer_handler+0x95/0x1e9
[   58.570548]  tcp_write_timer+0x2a/0x58

Check that daddr_cache is non-NULL before de-referencing.

Fixes: e086101b15 ("tcp: add a tracepoint for tcp retransmission")
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2017-10-16 15:32:07 -07:00 committed by David S. Miller
parent d4f4da3e13
commit 386fd5da40
1 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/trace/events/tcp.h
View File

@ -27,7 +27,6 @@ TRACE_EVENT(tcp_retransmit_skb,
),
TP_fast_assign(
struct ipv6_pinfo *np = inet6_sk(sk);
struct inet_sock *inet = inet_sk(sk);
struct in6_addr *pin6;
__be32 *p32;
@ -44,11 +43,12 @@ TRACE_EVENT(tcp_retransmit_skb,
p32 = (__be32 *) __entry->daddr;
*p32 = inet->inet_daddr;
if (np) {
/* IPv6 socket ? */
if (inet6_sk(sk)) {
pin6 = (struct in6_addr *)__entry->saddr_v6;
*pin6 = np->saddr;
*pin6 = sk->sk_v6_rcv_saddr;
pin6 = (struct in6_addr *)__entry->daddr_v6;
*pin6 = *(np->daddr_cache);
*pin6 = sk->sk_v6_daddr;
} else {
pin6 = (struct in6_addr *)__entry->saddr_v6;
ipv6_addr_set_v4mapped(inet->inet_saddr, pin6);