diff options
author | Elena Reshetova <elena.reshetova@intel.com> | 2017-10-20 10:37:37 +0300 |
---|---|---|
committer | Mike Snitzer <snitzer@redhat.com> | 2017-10-24 15:09:51 -0400 |
commit | 6bdd079610d3a5de0f4eb78d8015bd530c291cd7 (patch) | |
tree | 82b65fc46466466ecaa8339e0d52126d8bcb4dab /drivers/md | |
parent | b0b4d7c6752a45c545bcdce647ccfa8fb27f0a06 (diff) | |
download | linux-6bdd079610d3a5de0f4eb78d8015bd530c291cd7.tar.bz2 |
dm cache: convert dm_cache_metadata.ref_count from atomic_t to refcount_t
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable dm_cache_metadata.ref_count is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r-- | drivers/md/dm-cache-metadata.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c index 4a4e9c75fc4c..0d7212410e21 100644 --- a/drivers/md/dm-cache-metadata.c +++ b/drivers/md/dm-cache-metadata.c @@ -13,6 +13,7 @@ #include "persistent-data/dm-transaction-manager.h" #include <linux/device-mapper.h> +#include <linux/refcount.h> /*----------------------------------------------------------------*/ @@ -100,7 +101,7 @@ struct cache_disk_superblock { } __packed; struct dm_cache_metadata { - atomic_t ref_count; + refcount_t ref_count; struct list_head list; unsigned version; @@ -753,7 +754,7 @@ static struct dm_cache_metadata *metadata_open(struct block_device *bdev, } cmd->version = metadata_version; - atomic_set(&cmd->ref_count, 1); + refcount_set(&cmd->ref_count, 1); init_rwsem(&cmd->root_lock); cmd->bdev = bdev; cmd->data_block_size = data_block_size; @@ -791,7 +792,7 @@ static struct dm_cache_metadata *lookup(struct block_device *bdev) list_for_each_entry(cmd, &table, list) if (cmd->bdev == bdev) { - atomic_inc(&cmd->ref_count); + refcount_inc(&cmd->ref_count); return cmd; } @@ -862,7 +863,7 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev, void dm_cache_metadata_close(struct dm_cache_metadata *cmd) { - if (atomic_dec_and_test(&cmd->ref_count)) { + if (refcount_dec_and_test(&cmd->ref_count)) { mutex_lock(&table_lock); list_del(&cmd->list); mutex_unlock(&table_lock); |