5.4-stable review patch. If anyone has any objections, please let me know.
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From: Borislav Petkov (AMD) bp@alien8.de
commit 3ddf944b32f88741c303f0b21459dbb3872b8bc5 upstream.
Modifying a MCA bank's MCA_CTL bits which control which error types to be reported is done over
/sys/devices/system/machinecheck/ ├── machinecheck0 │ ├── bank0 │ ├── bank1 │ ├── bank10 │ ├── bank11 ...
sysfs nodes by writing the new bit mask of events to enable.
When the write is accepted, the kernel deletes all current timers and reinits all banks.
Doing that in parallel can lead to initializing a timer which is already armed and in the timer wheel, i.e., in use already:
ODEBUG: init active (active state 0) object: ffff888063a28000 object type: timer_list hint: mce_timer_fn+0x0/0x240 arch/x86/kernel/cpu/mce/core.c:2642 WARNING: CPU: 0 PID: 8120 at lib/debugobjects.c:514 debug_print_object+0x1a0/0x2a0 lib/debugobjects.c:514
Fix that by grabbing the sysfs mutex as the rest of the MCA sysfs code does.
Reported by: Yue Sun samsun1006219@gmail.com Reported by: xingwei lee xrivendell7@gmail.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Cc: stable@kernel.org Link: https://lore.kernel.org/r/CAEkJfYNiENwQY8yV1LYJ9LjJs%2Bx_-PqMv98gKig55=2vbzf... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/cpu/mce/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -2228,12 +2228,14 @@ static ssize_t set_bank(struct device *s return -EINVAL;
b = &per_cpu(mce_banks_array, s->id)[bank]; - if (!b->init) return -ENODEV;
b->ctl = new; + + mutex_lock(&mce_sysfs_mutex); mce_restart(); + mutex_unlock(&mce_sysfs_mutex);
return size; }