fs: fix UAF/GPF bug in nilfs_mdt_destroy

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>

diff --git a/fs/inode.c b/fs/inode.c
index 6462276dfdf04d9ce648b7a2f4a06faa727d9de0..5559a2983341c3aa466288cc4bbea64b548bec69 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -192,8 +192,6 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
        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);
 
@@ -228,11 +226,12 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
        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);