On 8/15/22 11:08 PM, Dongliang Mu wrote:

From: Dongliang Mu mudongliangabcd@gmail.com

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+J9nD1vf... Reported-by: butt3rflyh4ck butterflyhuangxx@gmail.com Reported-by: Hao Sun sunhao.th@gmail.com Reported-by: Jiacheng Xu stitch@zju.edu.cn Signed-off-by: Dongliang Mu mudongliangabcd@gmail.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: stable@vger.kernel.org

---

v1->v2: move security_inode_alloc at the very end according to Al Viro other than initializing i_private before security_inode_alloc. fs/inode.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c index 6462276dfdf0..49d1eb91728c 100644 --- 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);

@@ -228,6 +226,9 @@ int inode_init_always(struct super_block *sb, struct inode *inode) inode->i_fsnotify_mask = 0; #endif inode->i_flctx = NULL;

• if (security_inode_alloc(inode))

• goto out;
  

Seems like the out: label could be removed, and simply return -ENOMEM directly here, but that's just a nitpick.

-Eric

this_cpu_inc(nr_inodes); return 0;