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[PATCH] possible use-after-free of bio 

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 <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Jens Axboe 2005-04-16 15:25:40 -07:00 committed by Linus Torvalds
parent 9c340d80f6
commit 4a534f93b3
1 changed files with 3 additions and 2 deletions
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5
drivers/block/ll_rw_blk.c
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@ -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_t *q, struct bio *bio)
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);