From: Yufen Yu <yuyufen@xxxxxxxxxx> commit 77c301287ebae86cc71d03eb3806f271cb14da79 upstream. We have a test case like block/001 in blktests, which will create a scsi device by loading scsi_debug module and then try to delete the device by sysfs interface. At the same time, it may remove the scsi_debug module. And getting a invalid paging request BUG_ON as following: [ 34.625854] BUG: unable to handle page fault for address: ffffffffa0016bb8 [ 34.629189] Oops: 0000 [#1] SMP PTI [ 34.629618] CPU: 1 PID: 450 Comm: bash Tainted: G W 5.4.0-rc3+ #473 [ 34.632524] RIP: 0010:scsi_proc_hostdir_rm+0x5/0xa0 [ 34.643555] CR2: ffffffffa0016bb8 CR3: 000000012cd88000 CR4: 00000000000006e0 [ 34.644545] Call Trace: [ 34.644907] scsi_host_dev_release+0x6b/0x1f0 [ 34.645511] device_release+0x74/0x110 [ 34.646046] kobject_put+0x116/0x390 [ 34.646559] put_device+0x17/0x30 [ 34.647041] scsi_target_dev_release+0x2b/0x40 [ 34.647652] device_release+0x74/0x110 [ 34.648186] kobject_put+0x116/0x390 [ 34.648691] put_device+0x17/0x30 [ 34.649157] scsi_device_dev_release_usercontext+0x2e8/0x360 [ 34.649953] execute_in_process_context+0x29/0x80 [ 34.650603] scsi_device_dev_release+0x20/0x30 [ 34.651221] device_release+0x74/0x110 [ 34.651732] kobject_put+0x116/0x390 [ 34.652230] sysfs_unbreak_active_protection+0x3f/0x50 [ 34.652935] sdev_store_delete.cold.4+0x71/0x8f [ 34.653579] dev_attr_store+0x1b/0x40 [ 34.654103] sysfs_kf_write+0x3d/0x60 [ 34.654603] kernfs_fop_write+0x174/0x250 [ 34.655165] __vfs_write+0x1f/0x60 [ 34.655639] vfs_write+0xc7/0x280 [ 34.656117] ksys_write+0x6d/0x140 [ 34.656591] __x64_sys_write+0x1e/0x30 [ 34.657114] do_syscall_64+0xb1/0x400 [ 34.657627] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 34.658335] RIP: 0033:0x7f156f337130 During deleting scsi target, the scsi_debug module have been removed. Then, sdebug_driver_template belonged to the module cannot be accessd, resulting in scsi_proc_hostdir_rm() BUG_ON. To fix the bug, we add scsi_device_get() in sdev_store_delete() to try to increase refcount of module, avoiding the module been removed. Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/20191015130556.18061-1-yuyufen@xxxxxxxxxx Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx> Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx> Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/scsi/scsi_sysfs.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -723,6 +723,14 @@ sdev_store_delete(struct device *dev, st const char *buf, size_t count) { struct kernfs_node *kn; + struct scsi_device *sdev = to_scsi_device(dev); + + /* + * We need to try to get module, avoiding the module been removed + * during delete. + */ + if (scsi_device_get(sdev)) + return -ENODEV; kn = sysfs_break_active_protection(&dev->kobj, &attr->attr); WARN_ON_ONCE(!kn); @@ -737,9 +745,10 @@ sdev_store_delete(struct device *dev, st * state into SDEV_DEL. */ device_remove_file(dev, attr); - scsi_remove_device(to_scsi_device(dev)); + scsi_remove_device(sdev); if (kn) sysfs_unbreak_active_protection(kn); + scsi_device_put(sdev); return count; }; static DEVICE_ATTR(delete, S_IWUSR, NULL, sdev_store_delete);
