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btrfs: convert btrfs_root.refs 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 10:55:18 +02:00 committed by David Sterba
parent 089e77e10d
commit 0700cea7c8
3 changed files with 4 additions and 4 deletions
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2
fs/btrfs/ctree.h
View File

@ -1222,7 +1222,7 @@ struct btrfs_root {
dev_t anon_dev;
spinlock_t root_item_lock;
atomic_t refs;
refcount_t refs;
struct mutex delalloc_mutex;
spinlock_t delalloc_lock;

2
fs/btrfs/disk-io.c
View File

@ -1340,7 +1340,7 @@ static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
atomic_set(&root->log_writers, 0);
atomic_set(&root->log_batch, 0);
atomic_set(&root->orphan_inodes, 0);
atomic_set(&root->refs, 1);
refcount_set(&root->refs, 1);
atomic_set(&root->will_be_snapshoted, 0);
atomic64_set(&root->qgroup_meta_rsv, 0);
root->log_transid = 0;

4
fs/btrfs/disk-io.h
View File

@ -101,14 +101,14 @@ struct btrfs_root *btrfs_alloc_dummy_root(struct btrfs_fs_info *fs_info);
*/
static inline struct btrfs_root *btrfs_grab_fs_root(struct btrfs_root *root)
{
if (atomic_inc_not_zero(&root->refs))
if (refcount_inc_not_zero(&root->refs))
return root;
return NULL;
}
static inline void btrfs_put_fs_root(struct btrfs_root *root)
{
if (atomic_dec_and_test(&root->refs))
if (refcount_dec_and_test(&root->refs))
kfree(root);
}