| From | Tejun Heo <> | Subject | [PATCH 21/77] block: fix synchronization and limit check in blk_alloc_devt() | Date | Wed, 6 Feb 2013 11:39:53 -0800 |
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idr allocation in blk_alloc_devt() wasn't synchronized against lookup and removal, and its limit check was off by one - 1 << MINORBITS is the number of minors allowed, not the maximum allowed minor.
Add locking and rename MAX_EXT_DEVT to NR_EXT_DEVT and fix limit checking.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Jens Axboe <axboe@kernel.dk> Cc: stable@vger.kernel.org --- block/genhd.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c index 2eb64a3..b1f34d0 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -26,7 +26,7 @@ static DEFINE_MUTEX(block_class_lock); struct kobject *block_depr; /* for extended dynamic devt allocation, currently only one major is used */ -#define MAX_EXT_DEVT (1 << MINORBITS) +#define NR_EXT_DEVT (1 << MINORBITS) /* For extended devt allocation. ext_devt_mutex prevents look up * results from going away underneath its user. @@ -423,17 +423,18 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt) do { if (!idr_pre_get(&ext_devt_idr, GFP_KERNEL)) return -ENOMEM; + mutex_lock(&ext_devt_mutex); rc = idr_get_new(&ext_devt_idr, part, &idx); + if (!rc && idx >= NR_EXT_DEVT) { + idr_remove(&ext_devt_idr, idx); + rc = -EBUSY; + } + mutex_unlock(&ext_devt_mutex); } while (rc == -EAGAIN); if (rc) return rc; - if (idx > MAX_EXT_DEVT) { - idr_remove(&ext_devt_idr, idx); - return -EBUSY; - } - *devt = MKDEV(BLOCK_EXT_MAJOR, blk_mangle_minor(idx)); return 0; } -- 1.8.1
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