@@ -1436,6 +1436,16 @@ static int sd_open(struct block_device *bdev, fmode_t mode)
if (!scsi_block_when_processing_errors(sdev))
goto error_out;
+ /*
+ * Checking for changes to the device must not race with the device
+ * or its parent host being removed, so lock until sd_open returns.
+ */
+ mutex_lock(&sdev->host->scan_mutex);
+ if (sdev->sdev_state != SDEV_RUNNING) {
+ retval = -ERESTARTSYS;
+ goto unlock_scan_error_out;
+ }
+
if (sd_need_revalidate(bdev, sdkp))
sd_revalidate_disk(bdev->bd_disk);
@@ -1444,7 +1454,7 @@ static int sd_open(struct block_device *bdev, fmode_t mode)
*/
retval = -ENOMEDIUM;
if (sdev->removable && !sdkp->media_present && !(mode & FMODE_NDELAY))
- goto error_out;
+ goto unlock_scan_error_out;
/*
* If the device has the write protect tab set, have the open fail
@@ -1452,7 +1462,7 @@ static int sd_open(struct block_device *bdev, fmode_t mode)
*/
retval = -EROFS;
if (sdkp->write_prot && (mode & FMODE_WRITE))
- goto error_out;
+ goto unlock_scan_error_out;
/*
* It is possible that the disk changing stuff resulted in
@@ -1462,15 +1472,19 @@ static int sd_open(struct block_device *bdev, fmode_t mode)
*/
retval = -ENXIO;
if (!scsi_device_online(sdev))
- goto error_out;
+ goto unlock_scan_error_out;
if ((atomic_inc_return(&sdkp->openers) == 1) && sdev->removable) {
if (scsi_block_when_processing_errors(sdev))
scsi_set_medium_removal(sdev, SCSI_REMOVAL_PREVENT);
}
+ mutex_unlock(&sdev->host->scan_mutex);
return 0;
+unlock_scan_error_out:
+ mutex_unlock(&sdev->host->scan_mutex);
+
error_out:
scsi_disk_put(sdkp);
return retval;
sd and parent devices must not be removed as sd_open checks for events sd_need_revalidate and sd_revalidate_disk traverse the device path to check for event changes. If during this, e.g. the scsi host is being removed and its resources freed, this traversal crashes. Locking with scan_mutex for just a scsi disk open may seem blunt, but there does not seem to be a more granular option. Also opening /dev/sdX directly happens rarely enough that this shouldn't cause any issues. The issue occurred on an older kernel with the following trace: stack segment: 0000 [#1] PREEMPT SMP PTI CPU: 1 PID: 121457 Comm: python3 Not tainted 4.14.238hyLinux #1 Hardware name: ASUS All Series/H81M-D, BIOS 0601 02/20/2014 task: ffff888213dbb700 task.stack: ffffc90008c14000 RIP: 0010:kobject_get_path+0x2a/0xe0 ... Call Trace: kobject_uevent_env+0xe6/0x550 disk_check_events+0x101/0x160 disk_clear_events+0x75/0x100 check_disk_change+0x22/0x60 sd_open+0x70/0x170 [sd_mod] __blkdev_get+0x3fd/0x4b0 ? get_empty_filp+0x57/0x1b0 blkdev_get+0x11b/0x330 ? bd_acquire+0xc0/0xc0 do_dentry_open+0x1ef/0x320 ? __inode_permission+0x85/0xc0 path_openat+0x5cb/0x1500 ? terminate_walk+0xeb/0x100 do_filp_open+0x9b/0x110 ? __check_object_size+0xb4/0x190 ? do_sys_open+0x1bd/0x250 do_sys_open+0x1bd/0x250 do_syscall_64+0x67/0x120 entry_SYSCALL_64_after_hwframe+0x41/0xa6 and this commit fixed that issue, as there has been no other such synchronization in place since then, the issue should still be present in recent kernels. Signed-off-by: Christian Loehle <cloehle@hyperstone.com> --- drivers/scsi/sd.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)