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Commit 1601fbad authored by Mimi Zohar's avatar Mimi Zohar
Browse files

xattr: define vfs_getxattr_alloc and vfs_xattr_cmp 



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: default avatarMimi Zohar <zohar@us.ibm.com>
Acked-by: default avatarSerge Hallyn <serge.hallyn@ubuntu.com>
parent f381c272

fs/xattr.c

+58 −0
Original line number Diff line number Diff line
@@ -166,6 +166,64 @@ xattr_getsecurity(struct inode *inode, const char *name, void *value, 
}

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)

{

include/linux/xattr.h

+4 −1
Original line number Diff line number Diff line
@@ -84,7 +84,10 @@ 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 */