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    Subject[PATCH 09/17] fs, btrfs: convert btrfs_root.refs from atomic_t to refcount_t
    Date
    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>
    ---
    fs/btrfs/ctree.h | 2 +-
    fs/btrfs/disk-io.c | 2 +-
    fs/btrfs/disk-io.h | 4 ++--
    3 files changed, 4 insertions(+), 4 deletions(-)

    diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
    index 557af39..c01bfca 100644
    --- a/fs/btrfs/ctree.h
    +++ b/fs/btrfs/ctree.h
    @@ -1221,7 +1221,7 @@ 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;
    diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
    index 913df60..ca89ae3 100644
    --- a/fs/btrfs/disk-io.c
    +++ b/fs/btrfs/disk-io.c
    @@ -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);
    atomic_set(&root->qgroup_meta_rsv, 0);
    root->log_transid = 0;
    diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
    index 2e0ec29..21f1ceb 100644
    --- a/fs/btrfs/disk-io.h
    +++ b/fs/btrfs/disk-io.h
    @@ -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);
    }

    --
    2.7.4
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