From: Elena Reshetova <elena.reshetova@intel.com>
To: dm-devel@redhat.com
Cc: linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-raid@vger.kernel.org, kent.overstreet@gmail.com,
koverstreet@google.com, ejt@redhat.comg, snitzer@redhat.com,
shli@kernel.org, agk@redhat.com, peterz@infradead.org,
keescook@chromium.org,
Elena Reshetova <elena.reshetova@intel.com>
Subject: [PATCH 2/4] dm cache: convert dm_cache_metadata.ref_count from atomic_t to refcount_t
Date: Fri, 20 Oct 2017 10:37:37 +0300 [thread overview]
Message-ID: <1508485059-21881-3-git-send-email-elena.reshetova@intel.com> (raw)
In-Reply-To: <1508485059-21881-1-git-send-email-elena.reshetova@intel.com>
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>
---
drivers/md/dm-cache-metadata.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index 4a4e9c7..0d72124 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);
--
2.7.4
next prev parent reply other threads:[~2017-10-20 7:38 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-20 7:37 [PATCH 0/4] dm and bcache refcount conversions Elena Reshetova
2017-10-20 7:37 ` [PATCH 1/4] bcache: convert cached_dev.count from atomic_t to refcount_t Elena Reshetova
2017-10-20 18:39 ` Michael Lyle
2017-10-23 6:45 ` Reshetova, Elena
2017-10-20 7:37 ` Elena Reshetova [this message]
2017-10-20 7:37 ` [PATCH 3/4] dm: convert dm_dev_internal.count " Elena Reshetova
2017-11-23 15:49 ` [dm-devel] " Alasdair G Kergon
2017-11-24 7:36 ` Reshetova, Elena
2017-11-25 5:56 ` Mike Snitzer
2017-11-28 10:07 ` Reshetova, Elena
2017-11-28 19:02 ` Mike Snitzer
2017-11-29 8:05 ` Reshetova, Elena
2017-10-20 7:37 ` [PATCH 4/4] dm: convert table_device.count " Elena Reshetova
2017-11-23 15:19 ` Zdenek Kabelac
2017-11-24 8:29 ` Reshetova, Elena
2017-11-24 14:04 ` Alasdair G Kergon
2017-11-24 14:44 ` Reshetova, Elena
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