add-missing-hash-xattr-update

   1 ext4: add missing xattr hash update
   2
   3 From: Tahsin Erdogan <tahsin@google.com>
   4
   5 When updating an extended attribute, if the padded value sizes are the
   6 same, a shortcut is taken to avoid the bulk of the work. This was fine
   7 until the xattr hash update was moved inside ext4_xattr_set_entry().
   8 With that change, the hash update got missed in the shortcut case.
   9
  10 Thanks to ZhangYi (yizhang089@gmail.com) for root causing the problem.
  11
  12 Fixes: daf8328172df ("ext4: eliminate xattr entry e_hash recalculation for removes")
  13
  14 Reported-by: Miklos Szeredi <miklos@szeredi.hu>
  15 Signed-off-by: Tahsin Erdogan <tahsin@google.com>
  16 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  17 ---
  18  fs/ext4/xattr.c | 6 ++++--
  19  1 file changed, 4 insertions(+), 2 deletions(-)
  20
  21 diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
  22 index 82a5af9f6668..3dd970168448 100644
  23 --- a/fs/ext4/xattr.c
  24 +++ b/fs/ext4/xattr.c
  25 @@ -1543,7 +1543,7 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
  26                         /* Clear padding bytes. */
  27                         memset(val + i->value_len, 0, new_size - i->value_len);
  28                 }
  29 -               return 0;
  30 +               goto update_hash;
  31         }
  32
  33         /* Compute min_offs and last. */
  34 @@ -1707,6 +1707,7 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
  35                 here->e_value_size = cpu_to_le32(i->value_len);
  36         }
  37
  38 +update_hash:
  39         if (i->value) {
  40                 __le32 hash = 0;
  41
  42 @@ -1725,7 +1726,8 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
  43                                                      here->e_name_len,
  44                                                      &crc32c_hash, 1);
  45                 } else if (is_block) {
  46 -                       __le32 *value = s->base + min_offs - new_size;
  47 +                       __le32 *value = s->base + le16_to_cpu(
  48 +                                                       here->e_value_offs);
  49
  50                         hash = ext4_xattr_hash_entry(here->e_name,
  51                                                      here->e_name_len, value,
  52 --
  53 2.14.0.rc1.383.gd1ce394fe2-goog
  54
  55