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authorDamien Le Moal <damien.lemoal@opensource.wdc.com>2022-06-03 04:19:05 +0200
committerJens Axboe <axboe@kernel.dk>2022-06-03 07:02:37 +0200
commit41e46b3c2aa24f755b2ae9ec4ce931ba5f0d8532 (patch)
tree40575fecddd2d1e72ceae2f30a853665b0c75142 /block
parentblock: fix bio_clone_blkg_association() to associate with proper blkcg_gq (diff)
downloadlinux-41e46b3c2aa24f755b2ae9ec4ce931ba5f0d8532.tar.xz
linux-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')
-rw-r--r--block/blk-ia-ranges.c7
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 = {