Re: [syzbot] [serial?] possible deadlock in tty_port_tty_get

From: syzbot
Date: Sat Mar 25 2023 - 19:05:21 EST

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syzbot has found a reproducer for the following issue on:

HEAD commit: 65aca32efdcb Merge tag 'mm-hotfixes-stable-2023-03-24-17-0..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17b21b0ec80000
kernel config: https://syzkaller.appspot.com/x/.config?x=8ef27c4ff127cda5
dashboard link: https://syzkaller.appspot.com/bug?extid=223c7461c58c58a4cb10
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1591ba51c80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12ac6789c80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+223c7461c58c58a4cb10@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.3.0-rc3-syzkaller-00317-g65aca32efdcb #0 Not tainted
------------------------------------------------------
syz-executor930/5168 is trying to acquire lock:
ffffffff8c8e11e8 (zonelist_update_seq.seqcount){...-}-{0:0}, at: __alloc_pages+0x408/0x4a0 mm/page_alloc.c:5605

but task is already holding lock:
ffff888014325958 (&port->lock){-...}-{2:2}, at: tty_insert_flip_string_and_push_buffer+0x2f/0x160 drivers/tty/tty_buffer.c:628

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&port->lock){-...}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162
tty_port_tty_get+0x21/0xf0 drivers/tty/tty_port.c:327
tty_port_default_wakeup+0x15/0x40 drivers/tty/tty_port.c:68
serial8250_tx_chars+0x53e/0xdf0 drivers/tty/serial/8250/8250_port.c:1865
serial8250_handle_irq.part.0+0x460/0x870 drivers/tty/serial/8250/8250_port.c:1955
serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1928 [inline]
serial8250_default_handle_irq+0xb6/0x230 drivers/tty/serial/8250/8250_port.c:1975
serial8250_interrupt+0xfc/0x200 drivers/tty/serial/8250/8250_core.c:127
__handle_irq_event_percpu+0x22b/0x730 kernel/irq/handle.c:158
handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:210
handle_edge_irq+0x263/0xd00 kernel/irq/chip.c:819
generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
handle_irq arch/x86/kernel/irq.c:231 [inline]
__common_interrupt+0xa1/0x220 arch/x86/kernel/irq.c:250
common_interrupt+0xa8/0xd0 arch/x86/kernel/irq.c:240
asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:636
native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
arch_safe_halt arch/x86/include/asm/irqflags.h:86 [inline]
default_idle+0xf/0x20 arch/x86/kernel/process.c:703
default_idle_call+0x67/0xa0 kernel/sched/idle.c:97
cpuidle_idle_call kernel/sched/idle.c:170 [inline]
do_idle+0x31e/0x3e0 kernel/sched/idle.c:282
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:379
start_secondary+0x221/0x2b0 arch/x86/kernel/smpboot.c:264
secondary_startup_64_no_verify+0xce/0xdb

-> #2 (&port_lock_key
){-...}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:162
serial8250_console_write+0x4ba/0x1010 drivers/tty/serial/8250/8250_port.c:3401
console_emit_next_record kernel/printk/printk.c:2886 [inline]
console_flush_all+0x49c/0xcc0 kernel/printk/printk.c:2942
console_unlock+0xb8/0x1f0 kernel/printk/printk.c:3016
vprintk_emit+0x1bd/0x600 kernel/printk/printk.c:2316
vprintk+0x84/0xa0 kernel/printk/printk_safe.c:50
_printk+0xbf/0xf0 kernel/printk/printk.c:2337
register_console+0x7ef/0x10e0 kernel/printk/printk.c:3467
univ8250_console_init+0x38/0x50 drivers/tty/serial/8250/8250_core.c:688
console_init+0xba/0x5c0 kernel/printk/printk.c:3610
start_kernel+0x273/0x4d0 init/main.c:1081
secondary_startup_64_no_verify+0xce/0xdb

-> #1 (console_owner){....}-{0:0}:
console_lock_spinning_enable kernel/printk/printk.c:1867 [inline]
console_emit_next_record kernel/printk/printk.c:2880 [inline]
console_flush_all+0x472/0xcc0 kernel/printk/printk.c:2942
console_unlock+0xb8/0x1f0 kernel/printk/printk.c:3016
vprintk_emit+0x1bd/0x600 kernel/printk/printk.c:2316
vprintk+0x84/0xa0 kernel/printk/printk_safe.c:50
_printk+0xbf/0xf0 kernel/printk/printk.c:2337
build_zonelists+0x357/0x560 mm/page_alloc.c:6543
__build_all_zonelists+0x122/0x180 mm/page_alloc.c:6656
build_all_zonelists_init+0x1c/0x190 mm/page_alloc.c:6681
build_all_zonelists+0x4a/0x150 mm/page_alloc.c:6714
start_kernel+0xb7/0x4d0 init/main.c:975
secondary_startup_64_no_verify+0xce/0xdb

-> #0 (zonelist_update_seq.seqcount){...-}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3098 [inline]
check_prevs_add kernel/locking/lockdep.c:3217 [inline]
validate_chain kernel/locking/lockdep.c:3832 [inline]
__lock_acquire+0x2ec7/0x5d40 kernel/locking/lockdep.c:5056
lock_acquire kernel/locking/lockdep.c:5669 [inline]
lock_acquire+0x1af/0x520 kernel/locking/lockdep.c:5634
seqcount_lockdep_reader_access include/linux/seqlock.h:102 [inline]
read_seqbegin include/linux/seqlock.h:836 [inline]
zonelist_iter_begin mm/page_alloc.c:4765 [inline]
__alloc_pages_slowpath.constprop.0+0x15a/0x2170 mm/page_alloc.c:5086
__alloc_pages+0x408/0x4a0 mm/page_alloc.c:5605
__alloc_pages_node include/linux/gfp.h:237 [inline]
kmem_getpages mm/slab.c:1360 [inline]
cache_grow_begin+0x9b/0x3b0 mm/slab.c:2570
cache_alloc_refill+0x27f/0x380 mm/slab.c:2943
____cache_alloc mm/slab.c:3019 [inline]
____cache_alloc mm/slab.c:3002 [inline]
__do_cache_alloc mm/slab.c:3202 [inline]
slab_alloc_node mm/slab.c:3250 [inline]
__kmem_cache_alloc_node+0x360/0x3f0 mm/slab.c:3541
__do_kmalloc_node mm/slab_common.c:966 [inline]
__kmalloc+0x4e/0x190 mm/slab_common.c:980
kmalloc include/linux/slab.h:584 [inline]
tty_buffer_alloc+0x275/0x2f0 drivers/tty/tty_buffer.c:180
__tty_buffer_request_room+0x15b/0x2d0 drivers/tty/tty_buffer.c:278
tty_insert_flip_string_fixed_flag+0x90/0x250 drivers/tty/tty_buffer.c:327
tty_insert_flip_string include/linux/tty_flip.h:41 [inline]
tty_insert_flip_string_and_push_buffer+0x42/0x160 drivers/tty/tty_buffer.c:629
pty_write+0xda/0x100 drivers/tty/pty.c:118
ppp_async_push+0x5cb/0x1660 drivers/net/ppp/ppp_async.c:670
ppp_async_send+0xe2/0x110 drivers/net/ppp/ppp_async.c:638
__ppp_channel_push+0xe3/0x230 drivers/net/ppp/ppp_generic.c:2150
ppp_channel_push+0x1c2/0x250 drivers/net/ppp/ppp_generic.c:2177
ppp_write+0x22b/0x2d0 drivers/net/ppp/ppp_generic.c:523
do_loop_readv_writev fs/read_write.c:759 [inline]
do_loop_readv_writev fs/read_write.c:743 [inline]
do_iter_write+0x4ef/0x700 fs/read_write.c:863
vfs_writev+0x1aa/0x670 fs/read_write.c:934
do_pwritev fs/read_write.c:1031 [inline]
__do_sys_pwritev fs/read_write.c:1078 [inline]
__se_sys_pwritev fs/read_write.c:1073 [inline]
__x64_sys_pwritev+0x22f/0x310 fs/read_write.c:1073
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
zonelist_update_seq.seqcount --> &port_lock_key --> &port->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&port->lock);
lock(&port_lock_key);
lock(&port->lock);
lock(zonelist_update_seq.seqcount);

*** DEADLOCK ***

4 locks held by syz-executor930/5168:
#0: ffff888000630a48 (&pch->upl){.+..}-{2:2}, at: ppp_channel_push+0x28/0x250 drivers/net/ppp/ppp_generic.c:2171
#1: ffff8880006309e0 (&pch->downl){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]
#1: ffff8880006309e0 (&pch->downl){+...}-{2:2}, at: __ppp_channel_push+0x2a/0x230 drivers/net/ppp/ppp_generic.c:2146
#2: ffff8880283b8030 (&ap->xmit_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:355 [inline]
#2: ffff8880283b8030 (&ap->xmit_lock){+...}-{2:2}, at: ppp_async_push+0xb2/0x1660 drivers/net/ppp/ppp_async.c:663
#3: ffff888014325958 (&port->lock){-...}-{2:2}, at: tty_insert_flip_string_and_push_buffer+0x2f/0x160 drivers/tty/tty_buffer.c:628

stack backtrace:
CPU: 0 PID: 5168 Comm: syz-executor930 Not tainted 6.3.0-rc3-syzkaller-00317-g65aca32efdcb #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3098 [inline]
check_prevs_add kernel/locking/lockdep.c:3217 [inline]
validate_chain kernel/locking/lockdep.c:3832 [inline]
__lock_acquire+0x2ec7/0x5d40 kernel/locking/lockdep.c:5056
lock_acquire kernel/locking/lockdep.c:5669 [inline]
lock_acquire+0x1af/0x520 kernel/locking/lockdep.c:5634
seqcount_lockdep_reader_access include/linux/seqlock.h:102 [inline]
read_seqbegin include/linux/seqlock.h:836 [inline]
zonelist_iter_begin mm/page_alloc.c:4765 [inline]
__alloc_pages_slowpath.constprop.0+0x15a/0x2170 mm/page_alloc.c:5086
__alloc_pages+0x408/0x4a0 mm/page_alloc.c:5605
__alloc_pages_node include/linux/gfp.h:237 [inline]
kmem_getpages mm/slab.c:1360 [inline]
cache_grow_begin+0x9b/0x3b0 mm/slab.c:2570
cache_alloc_refill+0x27f/0x380 mm/slab.c:2943
____cache_alloc mm/slab.c:3019 [inline]
____cache_alloc mm/slab.c:3002 [inline]
__do_cache_alloc mm/slab.c:3202 [inline]
slab_alloc_node mm/slab.c:3250 [inline]
__kmem_cache_alloc_node+0x360/0x3f0 mm/slab.c:3541
__do_kmalloc_node mm/slab_common.c:966 [inline]
__kmalloc+0x4e/0x190 mm/slab_common.c:980
kmalloc include/linux/slab.h:584 [inline]
tty_buffer_alloc+0x275/0x2f0 drivers/tty/tty_buffer.c:180
__tty_buffer_request_room+0x15b/0x2d0 drivers/tty/tty_buffer.c:278
tty_insert_flip_string_fixed_flag+0x90/0x250 drivers/tty/tty_buffer.c:327
tty_insert_flip_string include/linux/tty_flip.h:41 [inline]
tty_insert_flip_string_and_push_buffer+0x42/0x160 drivers/tty/tty_buffer.c:629
pty_write+0xda/0x100 drivers/tty/pty.c:118
ppp_async_push+0x5cb/0x1660 drivers/net/ppp/ppp_async.c:670
ppp_async_send+0xe2/0x110 drivers/net/ppp/ppp_async.c:638
__ppp_channel_push+0xe3/0x230 drivers/net/ppp/ppp_generic.c:2150
ppp_channel_push+0x1c2/0x250 drivers/net/ppp/ppp_generic.c:2177
ppp_write+0x22b/0x2d0 drivers/net/ppp/ppp_generic.c:523
do_loop_readv_writev fs/read_write.c:759 [inline]
do_loop_readv_writev fs/read_write.c:743 [inline]
do_iter_write+0x4ef/0x700 fs/read_write.c:863
vfs_writev+0x1aa/0x670 fs/read_write.c:934
do_pwritev fs/read_write.c:1031 [inline]
__do_sys_pwritev fs/read_write.c:1078 [inline]
__se_sys_pwritev fs/read_write.c:1073 [inline]
__x64_sys_pwritev+0x22f/0x310 fs/read_write.c:1073
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f76be0b97d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 00 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffcac24418 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f76be0b97d9
RDX: 0000000000000003 RSI: 0000000020000380 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000004 R09: 000000000000000d
R10: 00000000000000f1 R11: 0000000000000246 R12: 00007fffcac24430
R13: 00000000000f4240 R14: 0000000000000000 R15: 0000000000000000
</TASK>

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Next in thread: syzbot: "Re: [syzbot] [serial?] possible deadlock in tty_port_tty_get"
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