[3/9] security,overlayfs: Provide security hook for copy up of xattrs for overlay file
diff mbox

Message ID 1468421095-22322-4-git-send-email-vgoyal@redhat.com
State New
Headers show

Commit Message

Vivek Goyal July 13, 2016, 2:44 p.m. UTC
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>
---
 fs/overlayfs/copy_up.c    |  7 +++++++
 include/linux/lsm_hooks.h | 10 ++++++++++
 include/linux/security.h  |  6 ++++++
 security/security.c       |  8 ++++++++
 4 files changed, 31 insertions(+)

Comments

Stephen Smalley July 14, 2016, 2:20 p.m. UTC | #1
On 07/13/2016 10:44 AM, Vivek Goyal wrote:
> 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>

> ---
>  fs/overlayfs/copy_up.c    |  7 +++++++
>  include/linux/lsm_hooks.h | 10 ++++++++++
>  include/linux/security.h  |  6 ++++++
>  security/security.c       |  8 ++++++++
>  4 files changed, 31 insertions(+)
> 
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index 8ebea18..68cefb2 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 c1f95be..84caead 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 c976d79..4a3b8bc 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 3d142aa..3321e31 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -733,6 +733,12 @@ 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;
> @@ -1671,6 +1677,8 @@ 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 =
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch
diff mbox

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 8ebea18..68cefb2 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 c1f95be..84caead 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 c976d79..4a3b8bc 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 3d142aa..3321e31 100644
--- a/security/security.c
+++ b/security/security.c
@@ -733,6 +733,12 @@  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;
@@ -1671,6 +1677,8 @@  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 =