[PATCH] USB Storage: close a race condition in disconnect near queuecommand
This patch started life as as534, and has been re-diffed against the latest
tree.
usb-storage has a small loophole, a window between the time queuecommand
accepts a new command and the time the control thread starts to execute
it. If disconnect is called during that window, the driver won't cancel
the pending command -- we've been relying on the SCSI core to cancel it
for us during host removal. But it's better for usb-storage to cancel
it; this avoids races and reduces reliance on the SCSI core.
Fortunately cancelling these commands is easy to do; the key is to do it
_before_ calling scsi_remove_host.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index 2557711..97b9ebb 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -833,6 +833,19 @@
/* Wait for the current command to finish, then remove the host */
down(&us->dev_semaphore);
up(&us->dev_semaphore);
+
+ /* queuecommand won't accept any new commands and the control
+ * thread won't execute a previously-queued command. If there
+ * is such a command pending, complete it with an error. */
+ if (us->srb) {
+ us->srb->result = DID_NO_CONNECT << 16;
+ scsi_lock(us_to_host(us));
+ us->srb->scsi_done(us->srb);
+ us->srb = NULL;
+ scsi_unlock(us_to_host(us));
+ }
+
+ /* Now we own no commands so it's safe to remove the SCSI host */
scsi_remove_host(us_to_host(us));
}