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xattr: define vfs_getxattr_alloc and vfs_xattr_cmp

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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@us.ibm.com>
Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com>
This commit is contained in:
Mimi Zohar 2011-03-09 14:23:34 -05:00
parent f381c27222
commit 1601fbad2b
2 changed files with 62 additions and 1 deletions
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58
fs/xattr.c
View File

@ -166,6 +166,64 @@ 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)
{

5
include/linux/xattr.h
View File

@ -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 */