2017-08-06 20:03:28

by Tahsin Erdogan

Subject: [PATCH] ext4: add missing xattr hash update

When updating an extended attribute, if the padded value sizes are the
same, a shortcut is taken to avoid the bulk of the work. This was fine
until the xattr hash update was moved inside ext4_xattr_set_entry().
With that change, the hash update got missed in the shortcut case.

Thanks to ZhangYi ([email protected]) for root causing the problem.

Fixes: daf8328172df ("ext4: eliminate xattr entry e_hash recalculation for removes")

Reported-by: Miklos Szeredi <[email protected]>
Signed-off-by: Tahsin Erdogan <[email protected]>
---
fs/ext4/xattr.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 82a5af9f6668..3dd970168448 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1543,7 +1543,7 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
/* Clear padding bytes. */
memset(val + i->value_len, 0, new_size - i->value_len);
}
- return 0;
+ goto update_hash;
}

/* Compute min_offs and last. */
@@ -1707,6 +1707,7 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
here->e_value_size = cpu_to_le32(i->value_len);
}

+update_hash:
if (i->value) {
__le32 hash = 0;

@@ -1725,7 +1726,8 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
here->e_name_len,
&crc32c_hash, 1);
} else if (is_block) {
- __le32 *value = s->base + min_offs - new_size;
+ __le32 *value = s->base + le16_to_cpu(
+ here->e_value_offs);

hash = ext4_xattr_hash_entry(here->e_name,
here->e_name_len, value,
--
2.14.0.rc1.383.gd1ce394fe2-goog

2017-08-14 12:31:21

by Theodore Ts'o

Subject: Re: [PATCH] ext4: add missing xattr hash update

On Sun, Aug 06, 2017 at 01:03:19PM -0700, Tahsin Erdogan wrote:
> When updating an extended attribute, if the padded value sizes are the
> same, a shortcut is taken to avoid the bulk of the work. This was fine
> until the xattr hash update was moved inside ext4_xattr_set_entry().
> With that change, the hash update got missed in the shortcut case.
>
> Thanks to ZhangYi ([email protected]) for root causing the problem.
>
> Fixes: daf8328172df ("ext4: eliminate xattr entry e_hash recalculation for removes")
>
> Reported-by: Miklos Szeredi <[email protected]>
> Signed-off-by: Tahsin Erdogan <[email protected]>

Thanks, applied.

- Ted