Commit 6b224899 authored by zhangyi (F)'s avatar zhangyi (F) Committed by Theodore Ts'o

ext4: do not try to set xattr into ea_inode if value is empty

Syzbot report a warning that ext4 may create an empty ea_inode if set
an empty extent attribute to a file on the file system which is no free
blocks left.

  WARNING: CPU: 6 PID: 10667 at fs/ext4/xattr.c:1640 ext4_xattr_set_entry+0x10f8/0x1114 fs/ext4/xattr.c:1640
  ...
  Call trace:
   ext4_xattr_set_entry+0x10f8/0x1114 fs/ext4/xattr.c:1640
   ext4_xattr_block_set+0x1d0/0x1b1c fs/ext4/xattr.c:1942
   ext4_xattr_set_handle+0x8a0/0xf1c fs/ext4/xattr.c:2390
   ext4_xattr_set+0x120/0x1f0 fs/ext4/xattr.c:2491
   ext4_xattr_trusted_set+0x48/0x5c fs/ext4/xattr_trusted.c:37
   __vfs_setxattr+0x208/0x23c fs/xattr.c:177
  ...

Now, ext4 try to store extent attribute into an external inode if
ext4_xattr_block_set() return -ENOSPC, but for the case of store an
empty extent attribute, store the extent entry into the extent
attribute block is enough. A simple reproduce below.

  fallocate test.img -l 1M
  mkfs.ext4 -F -b 2048 -O ea_inode test.img
  mount test.img /mnt
  dd if=/dev/zero of=/mnt/foo bs=2048 count=500
  setfattr -n "user.test" /mnt/foo

Reported-by: syzbot+98b881fdd8ebf45ab4ae@syzkaller.appspotmail.com
Fixes: 9c6e7853 ("ext4: reserve space for xattr entries/names")
Cc: stable@kernel.org
Signed-off-by: default avatarzhangyi (F) <yi.zhang@huawei.com>
Link: https://lore.kernel.org/r/20210305120508.298465-1-yi.zhang@huawei.comSigned-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 5dccdc5a
......@@ -2404,7 +2404,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
* external inode if possible.
*/
if (ext4_has_feature_ea_inode(inode->i_sb) &&
!i.in_inode) {
i.value_len && !i.in_inode) {
i.in_inode = 1;
goto retry_inode;
}
......
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