tmpfs: security xattr setting on inode creation
Adds to generic xattr support introduced in Linux 3.0 by implementing
initxattrs callback. This enables consulting of security attributes from
LSM and EVM when inode is created.
[hughd@google.com: moved under CONFIG_TMPFS_XATTR, with memcpy in shmem_xattr_alloc]
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/shmem.c b/mm/shmem.c
index b7e1955..7cc8083 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1178,6 +1178,12 @@
static const struct inode_operations shmem_symlink_inode_operations;
static const struct inode_operations shmem_short_symlink_operations;
+#ifdef CONFIG_TMPFS_XATTR
+static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
+#else
+#define shmem_initxattrs NULL
+#endif
+
static int
shmem_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
@@ -1490,7 +1496,7 @@
if (inode) {
error = security_inode_init_security(inode, dir,
&dentry->d_name,
- NULL, NULL);
+ shmem_initxattrs, NULL);
if (error) {
if (error != -EOPNOTSUPP) {
iput(inode);
@@ -1630,7 +1636,7 @@
return -ENOSPC;
error = security_inode_init_security(inode, dir, &dentry->d_name,
- NULL, NULL);
+ shmem_initxattrs, NULL);
if (error) {
if (error != -EOPNOTSUPP) {
iput(inode);
@@ -1704,6 +1710,66 @@
* filesystem level, though.
*/
+/*
+ * Allocate new xattr and copy in the value; but leave the name to callers.
+ */
+static struct shmem_xattr *shmem_xattr_alloc(const void *value, size_t size)
+{
+ struct shmem_xattr *new_xattr;
+ size_t len;
+
+ /* wrap around? */
+ len = sizeof(*new_xattr) + size;
+ if (len <= sizeof(*new_xattr))
+ return NULL;
+
+ new_xattr = kmalloc(len, GFP_KERNEL);
+ if (!new_xattr)
+ return NULL;
+
+ new_xattr->size = size;
+ memcpy(new_xattr->value, value, size);
+ return new_xattr;
+}
+
+/*
+ * Callback for security_inode_init_security() for acquiring xattrs.
+ */
+static int shmem_initxattrs(struct inode *inode,
+ const struct xattr *xattr_array,
+ void *fs_info)
+{
+ struct shmem_inode_info *info = SHMEM_I(inode);
+ const struct xattr *xattr;
+ struct shmem_xattr *new_xattr;
+ size_t len;
+
+ for (xattr = xattr_array; xattr->name != NULL; xattr++) {
+ new_xattr = shmem_xattr_alloc(xattr->value, xattr->value_len);
+ if (!new_xattr)
+ return -ENOMEM;
+
+ len = strlen(xattr->name) + 1;
+ new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
+ GFP_KERNEL);
+ if (!new_xattr->name) {
+ kfree(new_xattr);
+ return -ENOMEM;
+ }
+
+ memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
+ XATTR_SECURITY_PREFIX_LEN);
+ memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
+ xattr->name, len);
+
+ spin_lock(&info->lock);
+ list_add(&new_xattr->list, &info->xattr_list);
+ spin_unlock(&info->lock);
+ }
+
+ return 0;
+}
+
static int shmem_xattr_get(struct dentry *dentry, const char *name,
void *buffer, size_t size)
{
@@ -1731,24 +1797,17 @@
return ret;
}
-static int shmem_xattr_set(struct dentry *dentry, const char *name,
+static int shmem_xattr_set(struct inode *inode, const char *name,
const void *value, size_t size, int flags)
{
- struct inode *inode = dentry->d_inode;
struct shmem_inode_info *info = SHMEM_I(inode);
struct shmem_xattr *xattr;
struct shmem_xattr *new_xattr = NULL;
- size_t len;
int err = 0;
/* value == NULL means remove */
if (value) {
- /* wrap around? */
- len = sizeof(*new_xattr) + size;
- if (len <= sizeof(*new_xattr))
- return -ENOMEM;
-
- new_xattr = kmalloc(len, GFP_KERNEL);
+ new_xattr = shmem_xattr_alloc(value, size);
if (!new_xattr)
return -ENOMEM;
@@ -1757,9 +1816,6 @@
kfree(new_xattr);
return -ENOMEM;
}
-
- new_xattr->size = size;
- memcpy(new_xattr->value, value, size);
}
spin_lock(&info->lock);
@@ -1858,7 +1914,7 @@
if (size == 0)
value = ""; /* empty EA, do not remove */
- return shmem_xattr_set(dentry, name, value, size, flags);
+ return shmem_xattr_set(dentry->d_inode, name, value, size, flags);
}
@@ -1878,7 +1934,7 @@
if (err)
return err;
- return shmem_xattr_set(dentry, name, NULL, 0, XATTR_REPLACE);
+ return shmem_xattr_set(dentry->d_inode, name, NULL, 0, XATTR_REPLACE);
}
static bool xattr_is_trusted(const char *name)