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From: Serge E. Hallyn on 26 Apr 2010 15:00
Quoting Mimi Zohar (zohar(a)linux.vnet.ibm.com):
> vfs_getxattr_alloc() and vfs_xattr_cmp() are two new kernel xattr
> helper functions. vfs_getxattr_alloc() first allocates memory for
> the requested xattr and then retrieves it. vfs_xattr_cmp() compares
> a given value with the contents of an extended attribute.
>
> Signed-off-by: Mimi Zohar <zohar(a)us.ibm.com>

(Heh, *thought* I had a hole to point to, but nope, looks good)

Acked-by: Serge Hallyn <serue(a)us.ibm.com>

thanks,
-serge

>
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 46f87e8..341ad71 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -159,6 +159,64 @@ out_noalloc:
> }
> EXPORT_SYMBOL_GPL(xattr_getsecurity);
>
> +/*
> + * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
> + *
> + * Allocate memory, if not already allocated, or re-allocate correct size,
> + * before retrieving the extended attribute.
> + *
> + * Returns the result of alloc, if failed, or the getxattr operation.
> + */
> +ssize_t
> +vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
> + size_t xattr_size, gfp_t flags)
> +{
> + struct inode *inode = dentry->d_inode;
> + char *value = *xattr_value;
> + int error;
> +
> + error = xattr_permission(inode, name, MAY_READ);
> + if (error)
> + return error;
> +
> + if (!inode->i_op->getxattr)
> + return -EOPNOTSUPP;
> +
> + error = inode->i_op->getxattr(dentry, name, NULL, 0);
> + if (error < 0)
> + return error;
> +
> + if (!value || (error > xattr_size)) {
> + value = krealloc(*xattr_value, error + 1, flags);
> + if (!value)
> + return -ENOMEM;
> + memset(value, 0, error + 1);
> + }
> +
> + error = inode->i_op->getxattr(dentry, name, value, error);
> + *xattr_value = value;
> + return error;
> +}
> +
> +/* Compare an extended attribute value with the given value */
> +int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
> + const char *value, size_t size, gfp_t flags)
> +{
> + char *xattr_value = NULL;
> + int rc;
> +
> + rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
> + if (rc < 0)
> + return rc;
> +
> + if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
> + rc = -EINVAL;
> + else
> + rc = 0;
> + kfree(xattr_value);
> + return rc;
> +}
> +
> ssize_t
> vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
> {
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index d079bec..8698de3 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -68,7 +68,10 @@ ssize_t generic_getxattr(struct dentry *dentry, const char *name, void *buffer,
> ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size);
> int generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags);
> int generic_removexattr(struct dentry *dentry, const char *name);
> -
> +ssize_t vfs_getxattr_alloc(struct dentry *dentry, const char *name,
> + char **xattr_value, size_t size, gfp_t flags);
> +int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
> + const char *value, size_t size, gfp_t flags);
> #endif /* __KERNEL__ */
>
> #endif /* _LINUX_XATTR_H */
> --
> 1.6.6.1
>
> --
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