[PATCH] avoid NULL deference in ext2_xattr_get

[shenghui]

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.