ext4: fix use-after-free in ext4_orphan_cleanup

[ Upstream commit a71248b1accb2b42e4980afef4fa4a27fa0e36f5 ]

I caught a issue as follows:
==================================================================
 BUG: KASAN: use-after-free in __list_add_valid+0x28/0x1a0
 Read of size 8 at addr ffff88814b13f378 by task mount/710

 CPU: 1 PID: 710 Comm: mount Not tainted 6.1.0-rc3-next #370
 Call Trace:
  <TASK>
  dump_stack_lvl+0x73/0x9f
  print_report+0x25d/0x759
  kasan_report+0xc0/0x120
  __asan_load8+0x99/0x140
  __list_add_valid+0x28/0x1a0
  ext4_orphan_cleanup+0x564/0x9d0 [ext4]
  __ext4_fill_super+0x48e2/0x5300 [ext4]
  ext4_fill_super+0x19f/0x3a0 [ext4]
  get_tree_bdev+0x27b/0x450
  ext4_get_tree+0x19/0x30 [ext4]
  vfs_get_tree+0x49/0x150
  path_mount+0xaae/0x1350
  do_mount+0xe2/0x110
  __x64_sys_mount+0xf0/0x190
  do_syscall_64+0x35/0x80
  entry_SYSCALL_64_after_hwframe+0x63/0xcd
  </TASK>
 [...]
==================================================================

Above issue may happen as follows:
-------------------------------------
ext4_fill_super
  ext4_orphan_cleanup
   --- loop1: assume last_orphan is 12 ---
    list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan)
    ext4_truncate --> return 0
      ext4_inode_attach_jinode --> return -ENOMEM
    iput(inode) --> free inode<12>
   --- loop2: last_orphan is still 12 ---
    list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);
    // use inode<12> and trigger UAF

To solve this issue, we need to propagate the return value of
ext4_inode_attach_jinode() appropriately.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221102080633.1630225-1-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9380d9f79dea638fa7a5aada1bfd2c316ffe2a1f..cafa06114a1d119402d4e24848e6987c517e2d0e 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4556,7 +4556,8 @@ int ext4_truncate(struct inode *inode)
 
        /* If we zero-out tail of the page, we have to create jinode for jbd2 */
        if (inode->i_size & (inode->i_sb->s_blocksize - 1)) {
-               if (ext4_inode_attach_jinode(inode) < 0)
+               err = ext4_inode_attach_jinode(inode);
+               if (err)
                        goto out_trace;
        }