[PATCH 6.6 027/299] aoe: avoid potential deadlock at set_capacity

Greg Kroah-Hartman
2024-02-27T13:47:43Z

From: Maksim Kiselev <bigunclemax@gmail.com>

[ Upstream commit e169bd4fb2b36c4b2bee63c35c740c85daeb2e86 ]

Move set_capacity() outside of the section procected by (&d->lock).
To avoid possible interrupt unsafe locking scenario:

CPU0 CPU1
---- ----
[1] lock(&bdev->bd_size_lock);
local_irq_disable();
[2] lock(&d->lock);
[3] lock(&bdev->bd_size_lock);
<Interrupt>
[4] lock(&d->lock);

*** DEADLOCK ***

Where [1](&bdev->bd_size_lock) hold by zram_add()->set_capacity().
[2]lock(&d->lock) hold by aoeblk_gdalloc(). And aoeblk_gdalloc()
is trying to acquire [3](&bdev->bd_size_lock) at set_capacity() call.
In this situation an attempt to acquire [4]lock(&d->lock) from
aoecmd_cfg_rsp() will lead to deadlock.

So the simplest solution is breaking lock dependency
[2](&d->lock) -> [3](&bdev->bd_size_lock) by moving set_capacity()
outside.

Signed-off-by: Maksim Kiselev <bigunclemax@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240124072436.3745720-2-bigunclemax@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/aoe/aoeblk.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index cf6883756155a..37eff1c974515 100644
--- a/drivers/block/aoe/aoeblk.c
+++ b/drivers/block/aoe/aoeblk.c
@@ -333,6 +333,7 @@ aoeblk_gdalloc(void *vp)
struct gendisk *gd;
mempool_t *mp;
struct blk_mq_tag_set *set;
+ sector_t ssize;
ulong flags;
int late = 0;
int err;
@@ -395,7 +396,7 @@ aoeblk_gdalloc(void *vp)
gd->minors = AOE_PARTITIONS;
gd->fops = &aoe_bdops;
gd->private_data = d;
- set_capacity(gd, d->ssize);
+ ssize = d->ssize;
snprintf(gd->disk_name, sizeof gd->disk_name, "etherd/e%ld.%d",
d->aoemajor, d->aoeminor);

@@ -404,6 +405,8 @@ aoeblk_gdalloc(void *vp)

spin_unlock_irqrestore(&d->lock, flags);

+ set_capacity(gd, ssize);
+
err = device_add_disk(NULL, gd, aoe_attr_groups);
if (err)
goto out_disk_cleanup;
--
2.43.0