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    Subject[PATCH 4.9 018/159] fs: fix UAF/GPF bug in nilfs_mdt_destroy
    Date
    From: Dongliang Mu <mudongliangabcd@gmail.com>

    commit 2e488f13755ffbb60f307e991b27024716a33b29 upstream.

    In alloc_inode, inode_init_always() could return -ENOMEM if
    security_inode_alloc() fails, which causes inode->i_private
    uninitialized. Then nilfs_is_metadata_file_inode() returns
    true and nilfs_free_inode() wrongly calls nilfs_mdt_destroy(),
    which frees the uninitialized inode->i_private
    and leads to crashes(e.g., UAF/GPF).

    Fix this by moving security_inode_alloc just prior to
    this_cpu_inc(nr_inodes)

    Link: https://lkml.kernel.org/r/CAFcO6XOcf1Jj2SeGt=jJV59wmhESeSKpfR0omdFRq+J9nD1vfQ@mail.gmail.com
    Reported-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
    Reported-by: Hao Sun <sunhao.th@gmail.com>
    Reported-by: Jiacheng Xu <stitch@zju.edu.cn>
    Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
    Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: stable@vger.kernel.org
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/inode.c | 7 +++----
    1 file changed, 3 insertions(+), 4 deletions(-)

    --- a/fs/inode.c
    +++ b/fs/inode.c
    @@ -164,8 +164,6 @@ int inode_init_always(struct super_block
    inode->i_wb_frn_history = 0;
    #endif

    - if (security_inode_alloc(inode))
    - goto out;
    spin_lock_init(&inode->i_lock);
    lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);

    @@ -192,11 +190,12 @@ int inode_init_always(struct super_block
    inode->i_fsnotify_mask = 0;
    #endif
    inode->i_flctx = NULL;
    +
    + if (unlikely(security_inode_alloc(inode)))
    + return -ENOMEM;
    this_cpu_inc(nr_inodes);

    return 0;
    -out:
    - return -ENOMEM;
    }
    EXPORT_SYMBOL(inode_init_always);


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