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: a2247f19ee
("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>
This commit is contained in:
parent
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commit
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@ -54,13 +54,8 @@ static ssize_t blk_ia_range_sysfs_show(struct kobject *kobj,
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container_of(attr, struct blk_ia_range_sysfs_entry, attr);
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struct blk_independent_access_range *iar =
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container_of(kobj, struct blk_independent_access_range, kobj);
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ssize_t ret;
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mutex_lock(&iar->queue->sysfs_lock);
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ret = entry->show(iar, buf);
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mutex_unlock(&iar->queue->sysfs_lock);
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return ret;
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return entry->show(iar, buf);
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}
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static const struct sysfs_ops blk_ia_range_sysfs_ops = {
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