net/hamradio/6pack: use mod_timer() to rearm timers
commit 202700e30740c6568b5a6943662f3829566dd533 upstream.
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: 1da177e4c3f4 ("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>
[bwh: Backported to 3.16: Move initialisation of resync_t.data and
resync_t.function to sixpack_open(), as done by upstream commit
8e763de0b91d "net/hamradio/6pack: Convert timers to use timer_setup()".]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index 66e2b19..5e8aff8 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -551,12 +551,7 @@
/* Start resync timer again -- the TNC might be still absent */
-
- del_timer(&sp->resync_t);
- sp->resync_t.data = (unsigned long) sp;
- sp->resync_t.function = resync_tnc;
- 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)
@@ -567,11 +562,7 @@
sp->tty->ops->write(sp->tty, &inbyte, 1);
- del_timer(&sp->resync_t);
- sp->resync_t.data = (unsigned long) sp;
- sp->resync_t.function = resync_tnc;
- sp->resync_t.expires = jiffies + SIXP_RESYNC_TIMEOUT;
- add_timer(&sp->resync_t);
+ mod_timer(&sp->resync_t, jiffies + SIXP_RESYNC_TIMEOUT);
return 0;
}
@@ -654,6 +645,8 @@
sp->tx_t.data = (unsigned long) sp;
init_timer(&sp->resync_t);
+ sp->resync_t.function = resync_tnc;
+ sp->resync_t.data = (unsigned long) sp;
spin_unlock_bh(&sp->lock);
@@ -947,13 +940,8 @@
/* 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.data = (unsigned long) sp;
- sp->resync_t.function = resync_tnc;
- 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;
}
