The following commit has been merged into the efi/urgent branch of tip:

Commit-ID: 38fa3206bf441911258e5001ac8b6738693f8d82 Gitweb: https://git.kernel.org/tip/38fa3206bf441911258e5001ac8b6738693f8d82 Author: Zhang Jianhua chris.zjh@huawei.com AuthorDate: Thu, 23 Sep 2021 10:53:40 +08:00 Committer: Ard Biesheuvel ardb@kernel.org CommitterDate: Tue, 05 Oct 2021 13:07:01 +02:00

efi: Change down_interruptible() in virt_efi_reset_system() to down_trylock()

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.

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

diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c index 1410bea..f3e54f6 100644 --- 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 reset_type, 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;