[PATCH] signal: fix deadlock caused by calling printk() under sighand->siglock

From: Ye Weihua
Date: Fri Aug 26 2022 - 05:27:05 EST

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Next in thread: Eric W. Biederman: "Re: [PATCH] signal: fix deadlock caused by calling printk() under sighand->siglock"
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__dend_signal_locked() invokes __sigqueue_alloc() which may invoke a
normal printk() to print failure message. This can cause a deadlock in
the scenario reported by syz-bot below (test in 5.10):

CPU0 CPU1
---- ----
lock(&sighand->siglock);
lock(&tty->read_wait);
lock(&sighand->siglock);
lock(console_owner);

This patch specities __GFP_NOWARN to __sigqueue_alloc(), so that printk
will not be called, and this deadlock problem can be avoided.

Syzbot reported the following lockdep error:

======================================================
WARNING: possible circular locking dependency detected
5.10.0-04424-ga472e3c833d3 #1 Not tainted
------------------------------------------------------
syz-executor.2/31970 is trying to acquire lock:
ffffa00014066a60 (console_owner){-.-.}-{0:0}, at: console_trylock_spinning+0xf0/0x2e0 kernel/printk/printk.c:1854

but task is already holding lock:
ffff0000ddb38a98 (&sighand->siglock){-.-.}-{2:2}, at: force_sig_info_to_task+0x60/0x260 kernel/signal.c:1322

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #4 (&sighand->siglock){-.-.}-{2:2}:
validate_chain+0x6dc/0xb0c kernel/locking/lockdep.c:3728
__lock_acquire+0x498/0x940 kernel/locking/lockdep.c:4954
lock_acquire+0x228/0x580 kernel/locking/lockdep.c:5564
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xc0/0x15c kernel/locking/spinlock.c:159
__lock_task_sighand+0xf0/0x370 kernel/signal.c:1396
lock_task_sighand include/linux/sched/signal.h:699 [inline]
task_work_add+0x1f8/0x2a0 kernel/task_work.c:58
io_req_task_work_add+0x98/0x10c fs/io_uring.c:2115
__io_async_wake+0x338/0x780 fs/io_uring.c:4984
io_poll_wake+0x40/0x50 fs/io_uring.c:5461
__wake_up_common+0xcc/0x2a0 kernel/sched/wait.c:93
__wake_up_common_lock+0xd0/0x130 kernel/sched/wait.c:123
__wake_up+0x1c/0x24 kernel/sched/wait.c:142
pty_set_termios+0x1ac/0x2d0 drivers/tty/pty.c:286
tty_set_termios+0x310/0x46c drivers/tty/tty_ioctl.c:334
set_termios.part.0+0x2dc/0xa50 drivers/tty/tty_ioctl.c:414
set_termios drivers/tty/tty_ioctl.c:368 [inline]
tty_mode_ioctl+0x4f4/0xbec drivers/tty/tty_ioctl.c:736
n_tty_ioctl_helper+0x74/0x260 drivers/tty/tty_ioctl.c:883
n_tty_ioctl+0x80/0x3d0 drivers/tty/n_tty.c:2516
tty_ioctl+0x508/0x1100 drivers/tty/tty_io.c:2751
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl fs/ioctl.c:739 [inline]
__arm64_sys_ioctl+0x12c/0x18c fs/ioctl.c:739
__invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
el0_svc_common.constprop.0+0xf8/0x420 arch/arm64/kernel/syscall.c:155
do_el0_svc+0x50/0x120 arch/arm64/kernel/syscall.c:217
el0_svc+0x20/0x30 arch/arm64/kernel/entry-common.c:353
el0_sync_handler+0xe4/0x1e0 arch/arm64/kernel/entry-common.c:369
el0_sync+0x148/0x180 arch/arm64/kernel/entry.S:683

-> #3 (&tty->read_wait){....}-{2:2}:
validate_chain+0x6dc/0xb0c kernel/locking/lockdep.c:3728
__lock_acquire+0x498/0x940 kernel/locking/lockdep.c:4954
lock_acquire+0x228/0x580 kernel/locking/lockdep.c:5564
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0xa0/0x120 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:354 [inline]
io_poll_double_wake+0x158/0x30c fs/io_uring.c:5093
__wake_up_common+0xcc/0x2a0 kernel/sched/wait.c:93
__wake_up_common_lock+0xd0/0x130 kernel/sched/wait.c:123
__wake_up+0x1c/0x24 kernel/sched/wait.c:142
pty_close+0x1bc/0x330 drivers/tty/pty.c:68
tty_release+0x1e0/0x88c drivers/tty/tty_io.c:1761
__fput+0x1dc/0x500 fs/file_table.c:281
____fput+0x24/0x30 fs/file_table.c:314
task_work_run+0xf4/0x1ec kernel/task_work.c:151
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
do_notify_resume+0x378/0x410 arch/arm64/kernel/signal.c:718
work_pending+0xc/0x198

-> #2 (&tty->write_wait){....}-{2:2}:
validate_chain+0x6dc/0xb0c kernel/locking/lockdep.c:3728
__lock_acquire+0x498/0x940 kernel/locking/lockdep.c:4954
lock_acquire+0x228/0x580 kernel/locking/lockdep.c:5564
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xc0/0x15c kernel/locking/spinlock.c:159
__wake_up_common_lock+0xb0/0x130 kernel/sched/wait.c:122
__wake_up+0x1c/0x24 kernel/sched/wait.c:142
tty_wakeup+0x54/0xbc drivers/tty/tty_io.c:539
tty_port_default_wakeup+0x38/0x50 drivers/tty/tty_port.c:50
tty_port_tty_wakeup+0x3c/0x50 drivers/tty/tty_port.c:388
uart_write_wakeup+0x38/0x60 drivers/tty/serial/serial_core.c:106
pl011_tx_chars+0x530/0x5c0 drivers/tty/serial/amba-pl011.c:1418
pl011_start_tx_pio drivers/tty/serial/amba-pl011.c:1303 [inline]
pl011_start_tx+0x1b4/0x430 drivers/tty/serial/amba-pl011.c:1315
__uart_start.isra.0+0xb4/0xcc drivers/tty/serial/serial_core.c:127
uart_write+0x21c/0x460 drivers/tty/serial/serial_core.c:613
process_output_block+0x120/0x3ac drivers/tty/n_tty.c:590
n_tty_write+0x2c8/0x650 drivers/tty/n_tty.c:2383
do_tty_write drivers/tty/tty_io.c:1028 [inline]
file_tty_write.constprop.0+0x2d0/0x520 drivers/tty/tty_io.c:1118
tty_write drivers/tty/tty_io.c:1125 [inline]
redirected_tty_write+0xe4/0x104 drivers/tty/tty_io.c:1147
call_write_iter include/linux/fs.h:1960 [inline]
new_sync_write+0x264/0x37c fs/read_write.c:515
vfs_write+0x694/0x9d0 fs/read_write.c:602
ksys_write+0xfc/0x200 fs/read_write.c:655
__do_sys_write fs/read_write.c:667 [inline]
__se_sys_write fs/read_write.c:664 [inline]
__arm64_sys_write+0x50/0x60 fs/read_write.c:664
__invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
el0_svc_common.constprop.0+0xf8/0x420 arch/arm64/kernel/syscall.c:155
do_el0_svc+0x50/0x120 arch/arm64/kernel/syscall.c:217
el0_svc+0x20/0x30 arch/arm64/kernel/entry-common.c:353
el0_sync_handler+0xe4/0x1e0 arch/arm64/kernel/entry-common.c:369
el0_sync+0x148/0x180 arch/arm64/kernel/entry.S:683

-> #1 (&port_lock_key){-.-.}-{2:2}:
validate_chain+0x6dc/0xb0c kernel/locking/lockdep.c:3728
__lock_acquire+0x498/0x940 kernel/locking/lockdep.c:4954
lock_acquire+0x228/0x580 kernel/locking/lockdep.c:5564
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0xa0/0x120 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:354 [inline]
pl011_console_write+0x2f0/0x410 drivers/tty/serial/amba-pl011.c:2263
call_console_drivers.constprop.0+0x1f8/0x3b0 kernel/printk/printk.c:1932
console_unlock+0x36c/0x9ec kernel/printk/printk.c:2553
vprintk_emit+0x40c/0x4b0 kernel/printk/printk.c:2075
vprintk_default+0x48/0x54 kernel/printk/printk.c:2092
vprintk_func+0x1f0/0x40c kernel/printk/printk_safe.c:404
printk+0xbc/0xf0 kernel/printk/printk.c:2123
register_console+0x580/0x790 kernel/printk/printk.c:2905
uart_configure_port.constprop.0+0x4a0/0x4e0 drivers/tty/serial/serial_core.c:2431
uart_add_one_port+0x378/0x550 drivers/tty/serial/serial_core.c:2944
pl011_register_port+0xb4/0x210 drivers/tty/serial/amba-pl011.c:2686
pl011_probe+0x334/0x3ec drivers/tty/serial/amba-pl011.c:2736
amba_probe+0x14c/0x2f0 drivers/amba/bus.c:283
really_probe+0x210/0xa5c drivers/base/dd.c:562
driver_probe_device+0x1c8/0x280 drivers/base/dd.c:747
__device_attach_driver+0x18c/0x260 drivers/base/dd.c:853
bus_for_each_drv+0x120/0x1a0 drivers/base/bus.c:431
__device_attach+0x16c/0x3b4 drivers/base/dd.c:922
device_initial_probe+0x28/0x34 drivers/base/dd.c:971
bus_probe_device+0x124/0x13c drivers/base/bus.c:491
fw_devlink_resume+0x164/0x270 drivers/base/core.c:1601
of_platform_default_populate_init+0xf4/0x114 drivers/of/platform.c:543
do_one_initcall+0x11c/0x770 init/main.c:1217
do_initcall_level+0x364/0x388 init/main.c:1290
do_initcalls+0x90/0xc0 init/main.c:1306
do_basic_setup init/main.c:1326 [inline]
kernel_init_freeable+0x57c/0x63c init/main.c:1529
kernel_init+0x1c/0x20c init/main.c:1417
ret_from_fork+0x10/0x18 arch/arm64/kernel/entry.S:1034

-> #0 (console_owner){-.-.}-{0:0}:
check_prev_add+0xe0/0x105c kernel/locking/lockdep.c:2988
check_prevs_add+0x1c8/0x3d4 kernel/locking/lockdep.c:3113
validate_chain+0x6dc/0xb0c kernel/locking/lockdep.c:3728
__lock_acquire+0x498/0x940 kernel/locking/lockdep.c:4954
lock_acquire+0x228/0x580 kernel/locking/lockdep.c:5564
console_trylock_spinning+0x130/0x2e0 kernel/printk/printk.c:1875
vprintk_emit+0x268/0x4b0 kernel/printk/printk.c:2074
vprintk_default+0x48/0x54 kernel/printk/printk.c:2092
vprintk_func+0x1f0/0x40c kernel/printk/printk_safe.c:404
printk+0xbc/0xf0 kernel/printk/printk.c:2123
fail_dump lib/fault-inject.c:45 [inline]
should_fail+0x2a0/0x370 lib/fault-inject.c:146
__should_failslab+0x8c/0xe0 mm/failslab.c:33
should_failslab+0x14/0x2c mm/slab_common.c:1181
slab_pre_alloc_hook mm/slab.h:495 [inline]
slab_alloc_node mm/slub.c:2842 [inline]
slab_alloc mm/slub.c:2931 [inline]
kmem_cache_alloc+0x8c/0xe64 mm/slub.c:2936
__sigqueue_alloc+0x224/0x5a4 kernel/signal.c:437
__send_signal+0x700/0xeac kernel/signal.c:1121
send_signal+0x348/0x6a0 kernel/signal.c:1247
force_sig_info_to_task+0x184/0x260 kernel/signal.c:1339
force_sig_fault_to_task kernel/signal.c:1678 [inline]
force_sig_fault+0xb0/0xf0 kernel/signal.c:1685
arm64_force_sig_fault arch/arm64/kernel/traps.c:182 [inline]
arm64_notify_die arch/arm64/kernel/traps.c:208 [inline]
arm64_notify_die+0xdc/0x160 arch/arm64/kernel/traps.c:199
do_sp_pc_abort+0x4c/0x60 arch/arm64/mm/fault.c:794
el0_pc+0xd8/0x19c arch/arm64/kernel/entry-common.c:309
el0_sync_handler+0x12c/0x1e0 arch/arm64/kernel/entry-common.c:394
el0_sync+0x148/0x180 arch/arm64/kernel/entry.S:683

other info that might help us debug this:

Chain exists of:
console_owner --> &tty->read_wait --> &sighand->siglock

Signed-off-by: Ye Weihua <yeweihua4@xxxxxxxxxx>
---
kernel/signal.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 6f86fda5e432..3a3581739a6d 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1120,7 +1120,8 @@ static int __send_signal_locked(int sig, struct kernel_siginfo *info,
else
override_rlimit = 0;

- q = __sigqueue_alloc(sig, t, GFP_ATOMIC, override_rlimit, 0);
+ q = __sigqueue_alloc(sig, t, GFP_ATOMIC | __GFP_NOWARN,
+ override_rlimit, 0);

if (q) {
list_add_tail(&q->list, &pending->list);
--
2.17.1

Next message: Michael Walle: "Re: [PATCH net-next] net: phy: micrel: Adding SQI support for lan8814 phy"
Previous message: Shang XiaoJing: "[PATCH -next v2] sched/deadline: Add replenish_dl_new_period helper"
Next in thread: Eric W. Biederman: "Re: [PATCH] signal: fix deadlock caused by calling printk() under sighand->siglock"
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