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btrfs: convert btrfs_caching_control.count from atomic_t to refcount_t 

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Elena Reshetova 2017-03-03 10:55:14 +02:00 committed by David Sterba
parent e76edab7f0
commit 1e4f4714d5
2 changed files with 8 additions and 7 deletions
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3
fs/btrfs/ctree.h
View File

@ -39,6 +39,7 @@
#include <linux/security.h>
#include <linux/sizes.h>
#include <linux/dynamic_debug.h>
#include <linux/refcount.h>
#include "extent_io.h"
#include "extent_map.h"
#include "async-thread.h"
@ -518,7 +519,7 @@ struct btrfs_caching_control {
struct btrfs_work work;
struct btrfs_block_group_cache *block_group;
u64 progress;
atomic_t count;
refcount_t count;
};
/* Once caching_thread() finds this much free space, it will wake up waiters. */

12
fs/btrfs/extent-tree.c
View File

@ -316,14 +316,14 @@ get_caching_control(struct btrfs_block_group_cache *cache)
}
ctl = cache->caching_ctl;
atomic_inc(&ctl->count);
refcount_inc(&ctl->count);
spin_unlock(&cache->lock);
return ctl;
}
static void put_caching_control(struct btrfs_caching_control *ctl)
{
if (atomic_dec_and_test(&ctl->count))
if (refcount_dec_and_test(&ctl->count))
kfree(ctl);
}
@ -599,7 +599,7 @@ static int cache_block_group(struct btrfs_block_group_cache *cache,
init_waitqueue_head(&caching_ctl->wait);
caching_ctl->block_group = cache;
caching_ctl->progress = cache->key.objectid;
atomic_set(&caching_ctl->count, 1);
refcount_set(&caching_ctl->count, 1);
btrfs_init_work(&caching_ctl->work, btrfs_cache_helper,
caching_thread, NULL, NULL);
@ -620,7 +620,7 @@ static int cache_block_group(struct btrfs_block_group_cache *cache,
struct btrfs_caching_control *ctl;
ctl = cache->caching_ctl;
atomic_inc(&ctl->count);
refcount_inc(&ctl->count);
prepare_to_wait(&ctl->wait, &wait, TASK_UNINTERRUPTIBLE);
spin_unlock(&cache->lock);
@ -707,7 +707,7 @@ static int cache_block_group(struct btrfs_block_group_cache *cache,
}
down_write(&fs_info->commit_root_sem);
atomic_inc(&caching_ctl->count);
refcount_inc(&caching_ctl->count);
list_add_tail(&caching_ctl->list, &fs_info->caching_block_groups);
up_write(&fs_info->commit_root_sem);
@ -10416,7 +10416,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
&fs_info->caching_block_groups, list)
if (ctl->block_group == block_group) {
caching_ctl = ctl;
atomic_inc(&caching_ctl->count);
refcount_inc(&caching_ctl->count);
break;
}
}