[PATCH] avoid NULL deference in ext2_xattr_get

shenghui
2010-07-10T08:07:33Z

Hi,

I walked through ext2 code, and found one potential NULL deference
in ext2/xattr.c. The version is 2.6.35-rc4, while earlier versions have the
same problem.
If you configure EXT2_XATTR_DEBUG, you'll get:
# define ea_idebug(inode, f...) do { \
printk(KERN_DEBUG "inode %s:%ld: ", \
inode->i_sb->s_id, inode->i_ino); \
printk(f); \
printk("\n"); \
} while (0)

In ext2/xttr.c ext2_xattr_get, NULL pointer check is done after
ea_idebug call, so some may hit NULL deference here.
ext2_xattr_get(struct inode *inode, int name_index, const char *name,
void *buffer, size_t buffer_size)
{
struct buffer_head *bh = NULL;
struct ext2_xattr_entry *entry;
size_t name_len, size;
char *end;
int error;

ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
name_index, name, buffer, (long)buffer_size);

if (name == NULL)
return -EINVAL;

Following is my patch. Please check it.
The patch is against kernel 2.6.35-rc4.

>From adc1fa6535034db3b6d8deebda6ec7eaa8bfd2f8 Mon Sep 17 00:00:00 2001
From: Wang Sheng-Hui <crosslonelyover@gmail.com>
Date: Sat, 10 Jul 2010 16:05:53 +0800
Subject: [PATCH] avoid NULL deference in ext2_xattr_get

Signed-off-by: Wang Sheng-Hui <crosslonelyover@gmail.com>
---
fs/ext2/xattr.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index 7c39157..81ec1c6 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -156,11 +156,12 @@ ext2_xattr_get(struct inode *inode, int
name_index, const char *name,
char *end;
int error;

+ if (name == NULL)
+ return -EINVAL;
+
ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
name_index, name, buffer, (long)buffer_size);

- if (name == NULL)
- return -EINVAL;
down_read(&EXT2_I(inode)->xattr_sem);
error = -ENODATA;
if (!EXT2_I(inode)->i_file_acl)
--
1.6.3.3

--

Thanks and Best Regards,
shenghui