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authorVivek Goyal <vgoyal@redhat.com>2016-07-13 10:44:49 -0400
committerPaul Moore <paul@paul-moore.com>2016-08-08 20:42:13 -0400
commit121ab822ef21914adac2fa3730efeeb8fd762473 (patch)
tree7fd5f6947837b361c249ec976af17bee10b22a2e
parent56909eb3f559103196ecbf2c08c923e0804980fb (diff)
downloadlinux-121ab822ef21914adac2fa3730efeeb8fd762473.tar.bz2
security,overlayfs: Provide security hook for copy up of xattrs for overlay file
Provide a security hook which is called when xattrs of a file are being copied up. This hook is called once for each xattr and LSM can return 0 if the security module wants the xattr to be copied up, 1 if the security module wants the xattr to be discarded on the copy, -EOPNOTSUPP if the security module does not handle/manage the xattr, or a -errno upon an error. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Stephen Smalley <sds@tycho.nsa.gov> [PM: whitespace cleanup for checkpatch.pl] Signed-off-by: Paul Moore <paul@paul-moore.com>
-rw-r--r--fs/overlayfs/copy_up.c7
-rw-r--r--include/linux/lsm_hooks.h10
-rw-r--r--include/linux/security.h6
-rw-r--r--security/security.c8
4 files changed, 31 insertions, 0 deletions
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index c297b1f5a05e..cd65f12b3464 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -103,6 +103,13 @@ retry:
goto retry;
}
+ error = security_inode_copy_up_xattr(name);
+ if (error < 0 && error != -EOPNOTSUPP)
+ break;
+ if (error == 1) {
+ error = 0;
+ continue; /* Discard */
+ }
error = vfs_setxattr(new, name, value, size, 0);
if (error)
break;
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index cb69fc829053..57971229551b 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -410,6 +410,14 @@
* @src indicates the union dentry of file that is being copied up.
* @new pointer to pointer to return newly allocated creds.
* Returns 0 on success or a negative error code on error.
+ * @inode_copy_up_xattr:
+ * Filter the xattrs being copied up when a unioned file is copied
+ * up from a lower layer to the union/overlay layer.
+ * @name indicates the name of the xattr.
+ * Returns 0 to accept the xattr, 1 to discard the xattr, -EOPNOTSUPP if
+ * security module does not know about attribute or a negative error code
+ * to abort the copy up. Note that the caller is responsible for reading
+ * and writing the xattrs as this hook is merely a filter.
*
* Security hooks for file operations
*
@@ -1435,6 +1443,7 @@ union security_list_options {
size_t buffer_size);
void (*inode_getsecid)(struct inode *inode, u32 *secid);
int (*inode_copy_up)(struct dentry *src, struct cred **new);
+ int (*inode_copy_up_xattr)(const char *name);
int (*file_permission)(struct file *file, int mask);
int (*file_alloc_security)(struct file *file);
@@ -1707,6 +1716,7 @@ struct security_hook_heads {
struct list_head inode_listsecurity;
struct list_head inode_getsecid;
struct list_head inode_copy_up;
+ struct list_head inode_copy_up_xattr;
struct list_head file_permission;
struct list_head file_alloc_security;
struct list_head file_free_security;
diff --git a/include/linux/security.h b/include/linux/security.h
index c5b0ccd6c8b6..536fafdfa10a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -283,6 +283,7 @@ int security_inode_setsecurity(struct inode *inode, const char *name, const void
int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size);
void security_inode_getsecid(struct inode *inode, u32 *secid);
int security_inode_copy_up(struct dentry *src, struct cred **new);
+int security_inode_copy_up_xattr(const char *name);
int security_file_permission(struct file *file, int mask);
int security_file_alloc(struct file *file);
void security_file_free(struct file *file);
@@ -764,6 +765,11 @@ static inline int security_inode_copy_up(struct dentry *src, struct cred **new)
return 0;
}
+static inline int security_inode_copy_up_xattr(const char *name)
+{
+ return -EOPNOTSUPP;
+}
+
static inline int security_file_permission(struct file *file, int mask)
{
return 0;
diff --git a/security/security.c b/security/security.c
index f2a7f27bd3e9..a9e2bb9fb9d3 100644
--- a/security/security.c
+++ b/security/security.c
@@ -754,6 +754,12 @@ int security_inode_copy_up(struct dentry *src, struct cred **new)
}
EXPORT_SYMBOL(security_inode_copy_up);
+int security_inode_copy_up_xattr(const char *name)
+{
+ return call_int_hook(inode_copy_up_xattr, -EOPNOTSUPP, name);
+}
+EXPORT_SYMBOL(security_inode_copy_up_xattr);
+
int security_file_permission(struct file *file, int mask)
{
int ret;
@@ -1692,6 +1698,8 @@ struct security_hook_heads security_hook_heads = {
LIST_HEAD_INIT(security_hook_heads.inode_getsecid),
.inode_copy_up =
LIST_HEAD_INIT(security_hook_heads.inode_copy_up),
+ .inode_copy_up_xattr =
+ LIST_HEAD_INIT(security_hook_heads.inode_copy_up_xattr),
.file_permission =
LIST_HEAD_INIT(security_hook_heads.file_permission),
.file_alloc_security =