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net/hamradio/6pack: use mod_timer() to rearm timers 

Using del_timer() + add_timer() is generally unsafe on SMP,
as noticed by syzbot. Use mod_timer() instead.

kernel BUG at kernel/time/timer.c:1136!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 1026 Comm: kworker/u4:4 Not tainted 4.20.0+ #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound flush_to_ldisc
RIP: 0010:add_timer kernel/time/timer.c:1136 [inline]
RIP: 0010:add_timer+0xa81/0x1470 kernel/time/timer.c:1134
Code: 4d 89 7d 40 48 c7 85 70 fe ff ff 00 00 00 00 c7 85 7c fe ff ff ff ff ff ff 48 89 85 90 fe ff ff e9 e6 f7 ff ff e8 cf 42 12 00 <0f> 0b e8 c8 42 12 00 0f 0b e8 c1 42 12 00 4c 89 bd 60 fe ff ff e9
RSP: 0018:ffff8880a7fdf5a8 EFLAGS: 00010293
RAX: ffff8880a7846340 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff816f3ee1 RDI: ffff88808a514ff8
RBP: ffff8880a7fdf760 R08: 0000000000000007 R09: ffff8880a7846c58
R10: ffff8880a7846340 R11: 0000000000000000 R12: ffff88808a514ff8
R13: ffff88808a514ff8 R14: ffff88808a514dc0 R15: 0000000000000030
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000061c500 CR3: 00000000994d9000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 decode_prio_command drivers/net/hamradio/6pack.c:903 [inline]
 sixpack_decode drivers/net/hamradio/6pack.c:971 [inline]
 sixpack_receive_buf drivers/net/hamradio/6pack.c:457 [inline]
 sixpack_receive_buf+0xf9c/0x1470 drivers/net/hamradio/6pack.c:434
 tty_ldisc_receive_buf+0x164/0x1c0 drivers/tty/tty_buffer.c:465
 tty_port_default_receive_buf+0x114/0x190 drivers/tty/tty_port.c:38
 receive_buf drivers/tty/tty_buffer.c:481 [inline]
 flush_to_ldisc+0x3b2/0x590 drivers/tty/tty_buffer.c:533
 process_one_work+0xd0c/0x1ce0 kernel/workqueue.c:2153
 worker_thread+0x143/0x14a0 kernel/workqueue.c:2296
 kthread+0x357/0x430 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-01-02 04:24:20 -08:00 committed by David S. Miller
parent 53fe3ed19d
commit 202700e307
1 changed files with 4 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
drivers/net/hamradio/6pack.c
View File

@ -523,10 +523,7 @@ static void resync_tnc(struct timer_list *t)
/* Start resync timer again -- the TNC might be still absent */
del_timer(&sp->resync_t);
sp->resync_t.expires = jiffies + SIXP_RESYNC_TIMEOUT;
add_timer(&sp->resync_t);
mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT);
}
static inline int tnc_init(struct sixpack *sp)
@ -537,9 +534,7 @@ static inline int tnc_init(struct sixpack *sp)
sp->tty->ops->write(sp->tty, &inbyte, 1);
del_timer(&sp->resync_t);
sp->resync_t.expires = jiffies + SIXP_RESYNC_TIMEOUT;
add_timer(&sp->resync_t);
mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT);
return 0;
}
@ -897,11 +892,8 @@ static void decode_prio_command(struct sixpack *sp, unsigned char cmd)
/* if the state byte has been received, the TNC is present,
so the resync timer can be reset. */
if (sp->tnc_state == TNC_IN_SYNC) {
del_timer(&sp->resync_t);
sp->resync_t.expires = jiffies + SIXP_INIT_RESYNC_TIMEOUT;
add_timer(&sp->resync_t);
}
if (sp->tnc_state == TNC_IN_SYNC)
mod_timer(&sp->resync_t, jiffies + SIXP_INIT_RESYNC_TIMEOUT);
sp->status1 = cmd & SIXP_PRIO_DATA_MASK;
}