Messages in this thread Patch in this message | | | Date | Fri, 1 Jun 2007 11:22:49 +0400 | From | Alexey Dobriyan <> | Subject | [PATCH 2.6.16] Fix NULL bio crash in loop worker thread |
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After LOOP_SET_FD/LOOP_CLR_FD combo loop device's queue gets request handler which is persistent.
After, say
mount -t iso9660 /dev/loop0 /mnt # sic
this request handler is called directly with a) ->lo_state being Lo_unbound b) ->lo_pending being zero
Error path in loop_make_request() completes ->lo_bh_done completion which is persistent as well.
Now, let's start worker thread as usual. It'll set ->lo_pending to 1, don't wait for completion because it was already completed (brokenly), and will not get out of infinite loop because of ->lo_pending. Loop device doesn't have bios at this point and triggers BUG_ON.
So, don't complete ->lo_bh_done when loop device isn't setup fully.
Steps to reproduce:
#!/bin/sh -x ISO=1.iso mount -o loop $ISO /mnt umount /mnt mount -t iso9660 /dev/loop0 /mnt # sic mount -o loop $ISO /mnt
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru> ---
drivers/block/loop.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -521,7 +521,7 @@ static int loop_make_request(request_queue_t *q, struct bio *old_bio) spin_lock_irq(&lo->lo_lock); if (lo->lo_state != Lo_bound) - goto out; + goto out_not_bound; if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY))) goto out; lo->lo_pending++; @@ -533,6 +533,7 @@ static int loop_make_request(request_queue_t *q, struct bio *old_bio) out: if (lo->lo_pending == 0) complete(&lo->lo_bh_done); +out_not_bound: spin_unlock_irq(&lo->lo_lock); bio_io_error(old_bio, old_bio->bi_size); return 0; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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