4.20-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 202700e30740c6568b5a6943662f3829566dd533 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/hamradio/6pack.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-)
--- a/drivers/net/hamradio/6pack.c +++ b/drivers/net/hamradio/6pack.c @@ -523,10 +523,7 @@ static void resync_tnc(struct timer_list
/* 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 sixpac
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 s /* 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; }