can: j1939: j1939_sk_bind(): take priv after lock is held
syzbot reproduced following crash:
===============================================================================
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9844 Comm: syz-executor.0 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__lock_acquire+0x1254/0x4a00 kernel/locking/lockdep.c:3828
Code: 00 0f 85 96 24 00 00 48 81 c4 f0 00 00 00 5b 41 5c 41 5d 41 5e 41
5f 5d c3 48 b8 00 00 00 00 00 fc ff df 4c 89 f2 48 c1 ea 03 <80> 3c 02
00 0f 85 0b 28 00 00 49 81 3e 20 19 78 8a 0f 84 5f ee ff
RSP: 0018:
ffff888099c3fb48 EFLAGS:
00010006
RAX:
dffffc0000000000 RBX:
0000000000000000 RCX:
0000000000000000
RDX:
0000000000000218 RSI:
0000000000000000 RDI:
0000000000000001
RBP:
ffff888099c3fc60 R08:
0000000000000001 R09:
0000000000000001
R10:
fffffbfff146e1d0 R11:
ffff888098720400 R12:
00000000000010c0
R13:
0000000000000000 R14:
00000000000010c0 R15:
0000000000000000
FS:
00007f0559e98700(0000) GS:
ffff8880ae800000(0000)
knlGS:
0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
CR2:
00007fe4d89e0000 CR3:
0000000099606000 CR4:
00000000001406f0
DR0:
0000000000000000 DR1:
0000000000000000 DR2:
0000000000000000
DR3:
0000000000000000 DR6:
00000000fffe0ff0 DR7:
0000000000000400
Call Trace:
lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x33/0x50 kernel/locking/spinlock.c:175
spin_lock_bh include/linux/spinlock.h:343 [inline]
j1939_jsk_del+0x32/0x210 net/can/j1939/socket.c:89
j1939_sk_bind+0x2ea/0x8f0 net/can/j1939/socket.c:448
__sys_bind+0x239/0x290 net/socket.c:1648
__do_sys_bind net/socket.c:1659 [inline]
__se_sys_bind net/socket.c:1657 [inline]
__x64_sys_bind+0x73/0xb0 net/socket.c:1657
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a679
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:
00007f0559e97c78 EFLAGS:
00000246 ORIG_RAX:
0000000000000031
RAX:
ffffffffffffffda RBX:
0000000000000003 RCX:
000000000045a679
RDX:
0000000000000018 RSI:
0000000020000240 RDI:
0000000000000003
RBP:
000000000075bf20 R08:
0000000000000000 R09:
0000000000000000
R10:
0000000000000000 R11:
0000000000000246 R12:
00007f0559e986d4
R13:
00000000004c09e9 R14:
00000000004d37d0 R15:
00000000ffffffff
Modules linked in:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 9844 at kernel/locking/mutex.c:1419
mutex_trylock+0x279/0x2f0 kernel/locking/mutex.c:1427
===============================================================================
This issues was caused by null pointer deference. Where j1939_sk_bind()
was using currently not existing priv.
Possible scenario may look as following:
cpu0 cpu1
bind()
bind()
j1939_sk_bind()
j1939_sk_bind()
priv = jsk->priv;
priv = jsk->priv;
lock_sock(sock->sk);
priv = j1939_netdev_start(ndev);
j1939_jsk_add(priv, jsk);
jsk->priv = priv;
relase_sock(sock->sk);
lock_sock(sock->sk);
j1939_jsk_del(priv, jsk);
..... ooops ......
With this patch we move "priv = jsk->priv;" after the lock, to avoid
assigning of wrong priv pointer.
Reported-by: syzbot+99e9e1b200a1e363237d@syzkaller.appspotmail.com
Fixes:
9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: linux-stable <stable@vger.kernel.org> # >= v5.4
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>