Commit 4ddb85d3 authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Jens Axboe
Browse files

ataflop: remove ataflop_probe_lock mutex 



Commit bf9c0538 ("ataflop: use a separate gendisk for each media
format") introduced ataflop_probe_lock mutex, but forgot to unlock the
mutex when atari_floppy_init() (i.e. module loading) succeeded. This will
result in double lock deadlock if ataflop_probe() is called. Also,
unregister_blkdev() must not be called from atari_floppy_init() with
ataflop_probe_lock held when atari_floppy_init() failed, for
ataflop_probe() waits for ataflop_probe_lock with major_names_lock held
(i.e. AB-BA deadlock).

__register_blkdev() needs to be called last in order to avoid calling
ataflop_probe() when atari_floppy_init() is about to fail, for memory for
completing already-started ataflop_probe() safely will be released as soon
as atari_floppy_init() released ataflop_probe_lock mutex.

As with commit 8b52d8be ("loop: reorder loop_exit"),
unregister_blkdev() needs to be called first in order to avoid calling
ataflop_alloc_disk() from ataflop_probe() after del_gendisk() from
atari_floppy_exit().

By relocating __register_blkdev() / unregister_blkdev() as explained above,
we can remove ataflop_probe_lock mutex, for probe function and __exit
function are serialized by major_names_lock mutex.

Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: bf9c0538 ("ataflop: use a separate gendisk for each media format")
Reviewed-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Tested-by: default avatarMichael Schmitz <schmitzmic@gmail.com>
Link: https://lore.kernel.org/r/20211103230437.1639990-11-mcgrof@kernel.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent ed739191

drivers/block/ataflop.c

+27 −20
Original line number Diff line number Diff line
@@ -2008,8 +2008,6 @@ static int ataflop_alloc_disk(unsigned int drive, unsigned int type) 
	return 0;

}



static DEFINE_MUTEX(ataflop_probe_lock);



static void ataflop_probe(dev_t dev)

{

	int drive = MINOR(dev) & 3;
@@ -2020,14 +2018,32 @@ static void ataflop_probe(dev_t dev) 


	if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)

		return;

	mutex_lock(&ataflop_probe_lock);

	if (!unit[drive].disk[type]) {

		if (ataflop_alloc_disk(drive, type) == 0) {

			add_disk(unit[drive].disk[type]);

			unit[drive].registered[type] = true;

		}

	}

	mutex_unlock(&ataflop_probe_lock);

}



static void atari_floppy_cleanup(void)

{

	int i;

	int type;



	for (i = 0; i < FD_MAX_UNITS; i++) {

		for (type = 0; type < NUM_DISK_MINORS; type++) {

			if (!unit[i].disk[type])

				continue;

			del_gendisk(unit[i].disk[type]);

			blk_cleanup_queue(unit[i].disk[type]->queue);

			put_disk(unit[i].disk[type]);

		}

		blk_mq_free_tag_set(&unit[i].tag_set);

	}



	del_timer_sync(&fd_timer);

	atari_stram_free(DMABuffer);

}



static void atari_cleanup_floppy_disk(struct atari_floppy_struct *fs)
@@ -2053,11 +2069,6 @@ static int __init atari_floppy_init (void) 
		/* Amiga, Mac, ... don't have Atari-compatible floppy :-) */

		return -ENODEV;



	mutex_lock(&ataflop_probe_lock);

	ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);

	if (ret)

		goto out_unlock;



	for (i = 0; i < FD_MAX_UNITS; i++) {

		memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set));

		unit[i].tag_set.ops = &ataflop_mq_ops;
@@ -2113,7 +2124,12 @@ static int __init atari_floppy_init (void) 
	       UseTrackbuffer ? "" : "no ");

	config_types();



	return 0;

	ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);

	if (ret) {

		printk(KERN_ERR "atari_floppy_init: cannot register block device\n");

		atari_floppy_cleanup();

	}

	return ret;



err_out_dma:

	atari_stram_free(DMABuffer);
@@ -2121,9 +2137,6 @@ static int __init atari_floppy_init (void) 
	while (--i >= 0)

		atari_cleanup_floppy_disk(&unit[i]);



	unregister_blkdev(FLOPPY_MAJOR, "fd");

out_unlock:

	mutex_unlock(&ataflop_probe_lock);

	return ret;

}
@@ -2168,14 +2181,8 @@ __setup("floppy=", atari_floppy_setup); 


static void __exit atari_floppy_exit(void)

{

	int i;



	for (i = 0; i < FD_MAX_UNITS; i++)

		atari_cleanup_floppy_disk(&unit[i]);

	unregister_blkdev(FLOPPY_MAJOR, "fd");



	del_timer_sync(&fd_timer);

	atari_stram_free( DMABuffer );

	atari_floppy_cleanup();

}



module_init(atari_floppy_init)