2011-07-22 14:06:35

by Wang Sheng-Hui

Subject: [PATCH] ext2: check xattr name_len before acquiring sem lock in ext2_xattr_get

>From 667173a18b671896f933c5952fa211601d2e5ab0 Mon Sep 17 00:00:00 2001
From: Wang Sheng-Hui <[email protected]>
Date: Fri, 22 Jul 2011 08:50:13 -0500
Subject: [PATCH] ext2: check xattr name_len before acquiring sem lock in ext2_xattr_get

The patch is against 3.0.

In ext2_xattr_get, the code will acquire sem lock first, later check
the length of xattr name_len > 255. It's kind of time consuming, and
we should do the basic check before the time consuming acquiring sem
lock.

Signed-off-by: Wang Sheng-Hui <[email protected]>
---
fs/ext2/xattr.c | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index 5299706..d27b71f 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -161,6 +161,10 @@ ext2_xattr_get(struct inode *inode, int name_index, const char *name,

if (name == NULL)
return -EINVAL;
+ name_len = strlen(name);
+ if (name_len > 255)
+ return -ERANGE;
+
down_read(&EXT2_I(inode)->xattr_sem);
error = -ENODATA;
if (!EXT2_I(inode)->i_file_acl)
@@ -181,12 +185,8 @@ bad_block: ext2_error(inode->i_sb, "ext2_xattr_get",
error = -EIO;
goto cleanup;
}
- /* find named attribute */
- name_len = strlen(name);

- error = -ERANGE;
- if (name_len > 255)
- goto cleanup;
+ /* find named attribute */
entry = FIRST_ENTRY(bh);
while (!IS_LAST_ENTRY(entry)) {
struct ext2_xattr_entry *next =
--
1.7.1

2011-07-22 17:37:29

by Jan Kara

Subject: Re: [PATCH] ext2: check xattr name_len before acquiring sem lock in ext2_xattr_get

Hello,

On Fri 22-07-11 22:06:24, Wang Sheng-Hui wrote:
> From 667173a18b671896f933c5952fa211601d2e5ab0 Mon Sep 17 00:00:00 2001
> From: Wang Sheng-Hui <[email protected]>
> Date: Fri, 22 Jul 2011 08:50:13 -0500
> Subject: [PATCH] ext2: check xattr name_len before acquiring sem lock in ext2_xattr_get
>
> The patch is against 3.0.
>
> In ext2_xattr_get, the code will acquire sem lock first, later check
> the length of xattr name_len > 255. It's kind of time consuming, and
> we should do the basic check before the time consuming acquiring sem
> lock.
Well, but the check name_len > 255 is almost never true so it does not
really make a difference... But I see ext2_xattr_set() also checks the
length first so it probably makes sense from consistency point of view.
So I'll take the patch into my tree.

Honza
>
> Signed-off-by: Wang Sheng-Hui <[email protected]>
> ---
> fs/ext2/xattr.c | 10 +++++-----
> 1 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
> index 5299706..d27b71f 100644
> --- a/fs/ext2/xattr.c
> +++ b/fs/ext2/xattr.c
> @@ -161,6 +161,10 @@ ext2_xattr_get(struct inode *inode, int name_index, const char *name,
>
> if (name == NULL)
> return -EINVAL;
> + name_len = strlen(name);
> + if (name_len > 255)
> + return -ERANGE;
> +
> down_read(&EXT2_I(inode)->xattr_sem);
> error = -ENODATA;
> if (!EXT2_I(inode)->i_file_acl)
> @@ -181,12 +185,8 @@ bad_block: ext2_error(inode->i_sb, "ext2_xattr_get",
> error = -EIO;
> goto cleanup;
> }
> - /* find named attribute */
> - name_len = strlen(name);
>
> - error = -ERANGE;
> - if (name_len > 255)
> - goto cleanup;
> + /* find named attribute */
> entry = FIRST_ENTRY(bh);
> while (!IS_LAST_ENTRY(entry)) {
> struct ext2_xattr_entry *next =
> --
> 1.7.1
>
--
Jan Kara <[email protected]>
SUSE Labs, CR