* Re: net/kcm: WARNING in kcm_write_msgs
[not found] <CACT4Y+YSSKXzmJQ2J6nMCjD_32rgoqgLYkUjVGz8YswK1Uquvw@mail.gmail.com>
@ 2017-02-06 12:43 ` Dmitry Vyukov
2017-02-06 23:46 ` Cong Wang
0 siblings, 1 reply; 2+ messages in thread
From: Dmitry Vyukov @ 2017-02-06 12:43 UTC (permalink / raw)
To: David Miller, Tom Herbert, Cong Wang, Alexei Starovoitov,
Al Viro, Daniel Borkmann, netdev, LKML, Eric Dumazet
Cc: syzkaller
[resending as plain text]
Hello,
The following program triggers WARNING in kcm_write_msgs:
WARNING: CPU: 3 PID: 2936 at net/kcm/kcmsock.c:627
kcm_write_msgs+0x12e3/0x1b90 net/kcm/kcmsock.c:627
CPU: 3 PID: 2936 Comm: a.out Not tainted 4.10.0-rc6+ #209
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:15 [inline]
dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
panic+0x1fb/0x412 kernel/panic.c:179
__warn+0x1c4/0x1e0 kernel/panic.c:539
warn_slowpath_null+0x2c/0x40 kernel/panic.c:582
kcm_write_msgs+0x12e3/0x1b90 net/kcm/kcmsock.c:627
kcm_sendmsg+0x163a/0x2200 net/kcm/kcmsock.c:1029
sock_sendmsg_nosec net/socket.c:635 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:645
sock_write_iter+0x326/0x600 net/socket.c:848
new_sync_write fs/read_write.c:499 [inline]
__vfs_write+0x483/0x740 fs/read_write.c:512
vfs_write+0x187/0x530 fs/read_write.c:560
SYSC_write fs/read_write.c:607 [inline]
SyS_write+0xfb/0x230 fs/read_write.c:599
entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x434c09
RSP: 002b:00007fff40f2d7b8 EFLAGS: 00000217 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000401960 RCX: 0000000000434c09
RDX: 0000000000000000 RSI: 00000000208aaf27 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: 00007fff00000000
R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004002b0
R13: 0000000000401960 R14: 00000000004019f0 R15: 0000000000000000
// autogenerated by syzkaller (http://github.com/google/syzkaller)
#define _GNU_SOURCE
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/in.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifndef __NR_bpf
#define __NR_bpf 321
#endif
#ifndef AF_KCM
#define AF_KCM 0x29
#endif
int main()
{
syscall(__NR_mmap, 0x20000000ul, 0xfff000ul, 0x3ul, 0x32ul, -1, 0);
int sock = socket(AF_INET6, SOCK_STREAM, IPPROTO_IP);
(*(uint32_t*)0x20b4ffd0 = (uint32_t)0x1);
(*(uint32_t*)0x20b4ffd4 = (uint32_t)0x2);
(*(uint64_t*)0x20b4ffd8 = (uint64_t)0x20b4f000);
(*(uint64_t*)0x20b4ffe0 = (uint64_t)0x2015a000);
(*(uint32_t*)0x20b4ffe8 = (uint32_t)0x9);
(*(uint32_t*)0x20b4ffec = (uint32_t)0x80);
(*(uint64_t*)0x20b4fff0 = (uint64_t)0x20b4f000);
(*(uint32_t*)0x20b4fff8 = (uint32_t)0x0);
(*(uint8_t*)0x20b4f000 = (uint8_t)0xffffffffffffffb7);
(*(uint8_t*)0x20b4f001 = (uint8_t)0x0);
(*(uint16_t*)0x20b4f002 = (uint16_t)0x0);
(*(uint32_t*)0x20b4f004 = (uint32_t)0x0);
(*(uint8_t*)0x20b4f008 = (uint8_t)0x9595);
(*(uint8_t*)0x20b4f009 = (uint8_t)0x0);
(*(uint16_t*)0x20b4f00a = (uint16_t)0x0);
(*(uint32_t*)0x20b4f00c = (uint32_t)0x0);
(memcpy((void*)0x2015a000, "\x00\x8b", 2));
int bpf = syscall(__NR_bpf, 0x5ul, 0x20b4ffd0ul, 0x30ul, 0, 0,
0, 0, 0, 0);
int sock2 = syscall(__NR_socket, AF_KCM, 0x5ul, 0x0ul);
(*(uint32_t*)0x20b5c000 = sock);
(*(uint32_t*)0x20b5c004 = bpf);
syscall(__NR_ioctl, sock2, 0x89e0ul, 0x20b5c000ul);
syscall(__NR_write, sock2, 0x208aaf27ul, 0x0ul);
return 0;
}
On commit a572a1b999489efb591287632279c6c9eca3e4ed
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: net/kcm: WARNING in kcm_write_msgs
2017-02-06 12:43 ` net/kcm: WARNING in kcm_write_msgs Dmitry Vyukov
@ 2017-02-06 23:46 ` Cong Wang
0 siblings, 0 replies; 2+ messages in thread
From: Cong Wang @ 2017-02-06 23:46 UTC (permalink / raw)
To: Dmitry Vyukov
Cc: David Miller, Tom Herbert, Alexei Starovoitov, Al Viro,
Daniel Borkmann, netdev, LKML, Eric Dumazet, syzkaller
[-- Attachment #1: Type: text/plain, Size: 1406 bytes --]
On Mon, Feb 6, 2017 at 4:43 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
> [resending as plain text]
>
> Hello,
>
> The following program triggers WARNING in kcm_write_msgs:
>
> WARNING: CPU: 3 PID: 2936 at net/kcm/kcmsock.c:627
> kcm_write_msgs+0x12e3/0x1b90 net/kcm/kcmsock.c:627
> CPU: 3 PID: 2936 Comm: a.out Not tainted 4.10.0-rc6+ #209
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:15 [inline]
> dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
> panic+0x1fb/0x412 kernel/panic.c:179
> __warn+0x1c4/0x1e0 kernel/panic.c:539
> warn_slowpath_null+0x2c/0x40 kernel/panic.c:582
> kcm_write_msgs+0x12e3/0x1b90 net/kcm/kcmsock.c:627
> kcm_sendmsg+0x163a/0x2200 net/kcm/kcmsock.c:1029
> sock_sendmsg_nosec net/socket.c:635 [inline]
> sock_sendmsg+0xca/0x110 net/socket.c:645
> sock_write_iter+0x326/0x600 net/socket.c:848
> new_sync_write fs/read_write.c:499 [inline]
> __vfs_write+0x483/0x740 fs/read_write.c:512
> vfs_write+0x187/0x530 fs/read_write.c:560
> SYSC_write fs/read_write.c:607 [inline]
> SyS_write+0xfb/0x230 fs/read_write.c:599
> entry_SYSCALL_64_fastpath+0x1f/0xc2
[...]
> syscall(__NR_write, sock2, 0x208aaf27ul, 0x0ul);
Looks like len == 0 case is not handled correctly in kcm_sendmsg().
The attached patch fixes it, but I am not sure if it is correct in all
cases yet, the logic is complicated.
[-- Attachment #2: kcm.diff --]
[-- Type: text/plain, Size: 1730 bytes --]
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 7e08a4d..64f0e85 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -929,23 +929,25 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
goto out_error;
}
- /* New message, alloc head skb */
- head = alloc_skb(0, sk->sk_allocation);
- while (!head) {
- kcm_push(kcm);
- err = sk_stream_wait_memory(sk, &timeo);
- if (err)
- goto out_error;
-
+ if (msg_data_left(msg)) {
+ /* New message, alloc head skb */
head = alloc_skb(0, sk->sk_allocation);
- }
+ while (!head) {
+ kcm_push(kcm);
+ err = sk_stream_wait_memory(sk, &timeo);
+ if (err)
+ goto out_error;
- skb = head;
+ head = alloc_skb(0, sk->sk_allocation);
+ }
- /* Set ip_summed to CHECKSUM_UNNECESSARY to avoid calling
- * csum_and_copy_from_iter from skb_do_copy_data_nocache.
- */
- skb->ip_summed = CHECKSUM_UNNECESSARY;
+ skb = head;
+
+ /* Set ip_summed to CHECKSUM_UNNECESSARY to avoid calling
+ * csum_and_copy_from_iter from skb_do_copy_data_nocache.
+ */
+ skb->ip_summed = CHECKSUM_UNNECESSARY;
+ }
start:
while (msg_data_left(msg)) {
@@ -1018,10 +1020,12 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
if (eor) {
bool not_busy = skb_queue_empty(&sk->sk_write_queue);
- /* Message complete, queue it on send buffer */
- __skb_queue_tail(&sk->sk_write_queue, head);
- kcm->seq_skb = NULL;
- KCM_STATS_INCR(kcm->stats.tx_msgs);
+ if (head) {
+ /* Message complete, queue it on send buffer */
+ __skb_queue_tail(&sk->sk_write_queue, head);
+ kcm->seq_skb = NULL;
+ KCM_STATS_INCR(kcm->stats.tx_msgs);
+ }
if (msg->msg_flags & MSG_BATCH) {
kcm->tx_wait_more = true;
^ permalink raw reply related [flat|nested] 2+ messages in thread
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[not found] <CACT4Y+YSSKXzmJQ2J6nMCjD_32rgoqgLYkUjVGz8YswK1Uquvw@mail.gmail.com>
2017-02-06 12:43 ` net/kcm: WARNING in kcm_write_msgs Dmitry Vyukov
2017-02-06 23:46 ` Cong Wang
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