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| author | Damien Le Moal <damien.lemoal@opensource.wdc.com> | 2022-06-03 11:19:05 +0900 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-06-02 23:02:37 -0600 |
| commit | 41e46b3c2aa24f755b2ae9ec4ce931ba5f0d8532 (patch) | |
| tree | 40575fecddd2d1e72ceae2f30a853665b0c75142 /block/blk-ia-ranges.c | |
| parent | 22b106e5355d6e7a9c3b5cb5ed4ef22ae585ea94 (diff) | |
| download | lwn-41e46b3c2aa24f755b2ae9ec4ce931ba5f0d8532.tar.gz lwn-41e46b3c2aa24f755b2ae9ec4ce931ba5f0d8532.zip | |
block: Fix potential deadlock in blk_ia_range_sysfs_show()
When being read, a sysfs attribute is already protected against removal
with the kobject node active reference counter. As a result, in
blk_ia_range_sysfs_show(), there is no need to take the queue sysfs
lock when reading the value of a range attribute. Using the queue sysfs
lock in this function creates a potential deadlock situation with the
disk removal, something that a lockdep signals with a splat when the
device is removed:
[ 760.703551] Possible unsafe locking scenario:
[ 760.703551]
[ 760.703554] CPU0 CPU1
[ 760.703556] ---- ----
[ 760.703558] lock(&q->sysfs_lock);
[ 760.703565] lock(kn->active#385);
[ 760.703573] lock(&q->sysfs_lock);
[ 760.703579] lock(kn->active#385);
[ 760.703587]
[ 760.703587] *** DEADLOCK ***
Solve this by removing the mutex_lock()/mutex_unlock() calls from
blk_ia_range_sysfs_show().
Fixes: a2247f19ee1c ("block: Add independent access ranges support")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20220603021905.1441419-1-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-ia-ranges.c')
| -rw-r--r-- | block/blk-ia-ranges.c | 7 |
1 files changed, 1 insertions, 6 deletions
diff --git a/block/blk-ia-ranges.c b/block/blk-ia-ranges.c index 18c68d8b9138..56ed48d2954e 100644 --- a/block/blk-ia-ranges.c +++ b/block/blk-ia-ranges.c @@ -54,13 +54,8 @@ static ssize_t blk_ia_range_sysfs_show(struct kobject *kobj, container_of(attr, struct blk_ia_range_sysfs_entry, attr); struct blk_independent_access_range *iar = container_of(kobj, struct blk_independent_access_range, kobj); - ssize_t ret; - mutex_lock(&iar->queue->sysfs_lock); - ret = entry->show(iar, buf); - mutex_unlock(&iar->queue->sysfs_lock); - - return ret; + return entry->show(iar, buf); } static const struct sysfs_ops blk_ia_range_sysfs_ops = { |