[PATCH 5.10 033/103] efi: Change down_interruptible() in virt_efi_reset_system() to down_trylock()

Greg Kroah-Hartman
2021-10-18T13:40:50Z

From: Zhang Jianhua <chris.zjh@huawei.com>

commit 38fa3206bf441911258e5001ac8b6738693f8d82 upstream.

While reboot the system by sysrq, the following bug will be occur.

BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:90
in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 10052, name: rc.shutdown
CPU: 3 PID: 10052 Comm: rc.shutdown Tainted: G W O 5.10.0 #1
Call trace:
dump_backtrace+0x0/0x1c8
show_stack+0x18/0x28
dump_stack+0xd0/0x110
___might_sleep+0x14c/0x160
__might_sleep+0x74/0x88
down_interruptible+0x40/0x118
virt_efi_reset_system+0x3c/0xd0
efi_reboot+0xd4/0x11c
machine_restart+0x60/0x9c
emergency_restart+0x1c/0x2c
sysrq_handle_reboot+0x1c/0x2c
__handle_sysrq+0xd0/0x194
write_sysrq_trigger+0xbc/0xe4
proc_reg_write+0xd4/0xf0
vfs_write+0xa8/0x148
ksys_write+0x6c/0xd8
__arm64_sys_write+0x18/0x28
el0_svc_common.constprop.3+0xe4/0x16c
do_el0_svc+0x1c/0x2c
el0_svc+0x20/0x30
el0_sync_handler+0x80/0x17c
el0_sync+0x158/0x180

The reason for this problem is that irq has been disabled in
machine_restart() and then it calls down_interruptible() in
virt_efi_reset_system(), which would occur sleep in irq context,
it is dangerous! Commit 99409b935c9a("locking/semaphore: Add
might_sleep() to down_*() family") add might_sleep() in
down_interruptible(), so the bug info is here. down_trylock()
can solve this problem, cause there is no might_sleep.

--------

Cc: <stable@vger.kernel.org>
Signed-off-by: Zhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/firmware/efi/runtime-wrappers.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -414,7 +414,7 @@ static void virt_efi_reset_system(int re
unsigned long data_size,
efi_char16_t *data)
{
- if (down_interruptible(&efi_runtime_lock)) {
+ if (down_trylock(&efi_runtime_lock)) {
pr_warn("failed to invoke the reset_system() runtime service:\n"
"could not get exclusive access to the firmware\n");
return;