[PATCH 5.15 789/917] ataflop: remove ataflop_probe_lock mutex

Greg Kroah-Hartman
2021-11-16T00:02:17Z

From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>

[ Upstream commit 4ddb85d36613c45bde00d368bf9f357bd0708a0c ]

Commit bf9c0538e485b591 ("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 8b52d8be86d72308 ("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: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: bf9c0538e485b591 ("ataflop: use a separate gendisk for each media format")
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Link: https://lore.kernel.org/r/20211103230437.1639990-11-mcgrof@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/ataflop.c | 47 +++++++++++++++++++++++------------------
1 file changed, 27 insertions(+), 20 deletions(-)

diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index 123ad58193098..aab48b292a3bb 100644
--- a/drivers/block/ataflop.c
+++ b/drivers/block/ataflop.c
@@ -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;
@@ -2111,15 +2122,17 @@ 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:
while (--i >= 0)
atari_cleanup_floppy_disk(&unit[i]);

- unregister_blkdev(FLOPPY_MAJOR, "fd");
-out_unlock:
- mutex_unlock(&ataflop_probe_lock);
return ret;
}

@@ -2164,14 +2177,8 @@ __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)
--
2.33.0