• Seunghun Han's avatar
    x86/MCE: Serialize sysfs changes · b3b7c479
    Seunghun Han authored
    The check_interval file in
    
      /sys/devices/system/machinecheck/machinecheck<cpu number>
    
    directory is a global timer value for MCE polling. If it is changed by one
    CPU, mce_restart() broadcasts the event to other CPUs to delete and restart
    the MCE polling timer and __mcheck_cpu_init_timer() reinitializes the
    mce_timer variable.
    
    If more than one CPU writes a specific value to the check_interval file
    concurrently, mce_timer is not protected from such concurrent accesses and
    all kinds of explosions happen. Since only root can write to those sysfs
    variables, the issue is not a big deal security-wise.
    
    However, concurrent writes to these configuration variables is void of
    reason so the proper thing to do is to serialize the access with a mutex.
    
    Boris:
    
     - Make store_int_with_restart() use device_store_ulong() to filter out
       negative intervals
     - Limit min interval to 1 second
     - Correct locking
     - Massage commit message
    Signed-off-by: default avatarSeunghun Han <kkamagui@gmail.com>
    Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: linux-edac <linux-edac@vger.kernel.org>
    Cc: stable@vger.kernel.org
    Link: http://lkml.kernel.org/r/20180302202706.9434-1-kkamagui@gmail.com
    b3b7c479
mce.c 56.6 KB