From: Jens Axboe There is a possibility that a bio will be accessed after it has been freed on SCSI. It happens if you submit a bio with BIO_SYNC marked and the auto-unplugging kicks the request_fn, SCSI re-enables interrupts in-between so if the request completes between the add_request() in __make_request() and the bio_sync() call, we could be looking at a dead bio. It's a slim race, but it has been triggered in the Real World. So assign bio_sync() to a local variable instead. Signed-off-by: Jens Axboe Signed-off-by: Andrew Morton --- 25-akpm/drivers/block/ll_rw_blk.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff -puN drivers/block/ll_rw_blk.c~possible-use-after-free-of-bio drivers/block/ll_rw_blk.c --- 25/drivers/block/ll_rw_blk.c~possible-use-after-free-of-bio Wed Apr 6 16:23:56 2005 +++ 25-akpm/drivers/block/ll_rw_blk.c Wed Apr 6 16:23:56 2005 @@ -2559,7 +2559,7 @@ EXPORT_SYMBOL(__blk_attempt_remerge); static int __make_request(request_queue_t *q, struct bio *bio) { struct request *req, *freereq = NULL; - int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err; + int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err, sync; sector_t sector; sector = bio->bi_sector; @@ -2567,6 +2567,7 @@ static int __make_request(request_queue_ cur_nr_sectors = bio_cur_sectors(bio); rw = bio_data_dir(bio); + sync = bio_sync(bio); /* * low level driver can indicate that it wants pages above a @@ -2698,7 +2699,7 @@ get_rq: out: if (freereq) __blk_put_request(q, freereq); - if (bio_sync(bio)) + if (sync) __generic_unplug_device(q); spin_unlock_irq(q->queue_lock); _