[5/8] SELinux: Stub in copy-up handling
diff mbox

Message ID 20150618133254.12722.33339.stgit@warthog.procyon.org.uk
State New
Headers show

Commit Message

David Howells June 18, 2015, 1:32 p.m. UTC
Provide stubs for union/overlay copy-up handling.  The xattr copy up stub
discards lower SELinux xattrs rather than letting them be copied up so that
the security label on the copy doesn't get corrupted.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 security/selinux/hooks.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)


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Comments

Stephen Smalley June 18, 2015, 2:44 p.m. UTC | #1
On 06/18/2015 09:32 AM, David Howells wrote:
> Provide stubs for union/overlay copy-up handling.  The xattr copy up stub
> discards lower SELinux xattrs rather than letting them be copied up so that
> the security label on the copy doesn't get corrupted.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
> 
>  security/selinux/hooks.c |   16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index ffa5a642629a..c5d893e2ff23 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3200,6 +3200,20 @@ static void selinux_inode_getsecid(const struct inode *inode, u32 *secid)
>  	*secid = isec->sid;
>  }
>  
> +static int selinux_inode_copy_up(struct dentry *src, struct dentry *dst)
> +{
> +	return 0;
> +}
> +
> +static int selinux_inode_copy_up_xattr(struct dentry *src, struct dentry *dst,
> +				       const char *name, void *value,
> +				       size_t *size)
> +{
> +	if (strcmp(name, XATTR_NAME_SELINUX) == 0)
> +		return 1; /* Discard */
> +	return 0;
> +}
> +

(expanded cc list)

I'm not sure we never want to copy up the SELinux attribute.  See my
other email about ecryptfs and supporting per-file labeling and
consistent access control over the upper and lower inodes.

>  /* file security operations */
>  
>  static int selinux_revalidate_file_permission(struct file *file, int mask)
> @@ -5917,6 +5931,8 @@ static struct security_operations selinux_ops = {
>  	.inode_setsecurity =		selinux_inode_setsecurity,
>  	.inode_listsecurity =		selinux_inode_listsecurity,
>  	.inode_getsecid =		selinux_inode_getsecid,
> +	.inode_copy_up =		selinux_inode_copy_up,
> +	.inode_copy_up_xattr =		selinux_inode_copy_up_xattr,
>  
>  	.file_permission =		selinux_file_permission,
>  	.file_alloc_security =		selinux_file_alloc_security,
> 
> 

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Casey Schaufler June 18, 2015, 3:34 p.m. UTC | #2
On 6/18/2015 6:32 AM, David Howells wrote:
> Provide stubs for union/overlay copy-up handling.  The xattr copy up stub
> discards lower SELinux xattrs rather than letting them be copied up so that
> the security label on the copy doesn't get corrupted.

Are you planning to do this for Smack, too?

>
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
>
>  security/selinux/hooks.c |   16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index ffa5a642629a..c5d893e2ff23 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3200,6 +3200,20 @@ static void selinux_inode_getsecid(const struct inode *inode, u32 *secid)
>  	*secid = isec->sid;
>  }
>  
> +static int selinux_inode_copy_up(struct dentry *src, struct dentry *dst)
> +{
> +	return 0;
> +}
> +
> +static int selinux_inode_copy_up_xattr(struct dentry *src, struct dentry *dst,
> +				       const char *name, void *value,
> +				       size_t *size)
> +{
> +	if (strcmp(name, XATTR_NAME_SELINUX) == 0)
> +		return 1; /* Discard */
> +	return 0;
> +}
> +
>  /* file security operations */
>  
>  static int selinux_revalidate_file_permission(struct file *file, int mask)
> @@ -5917,6 +5931,8 @@ static struct security_operations selinux_ops = {
>  	.inode_setsecurity =		selinux_inode_setsecurity,
>  	.inode_listsecurity =		selinux_inode_listsecurity,
>  	.inode_getsecid =		selinux_inode_getsecid,
> +	.inode_copy_up =		selinux_inode_copy_up,
> +	.inode_copy_up_xattr =		selinux_inode_copy_up_xattr,
>  
>  	.file_permission =		selinux_file_permission,
>  	.file_alloc_security =		selinux_file_alloc_security,
>
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David Howells June 18, 2015, 4:51 p.m. UTC | #3
Stephen Smalley <sds@tycho.nsa.gov> wrote:

> I'm not sure we never want to copy up the SELinux attribute.  See my
> other email about ecryptfs and supporting per-file labeling and
> consistent access control over the upper and lower inodes.

Yes.  That's why there are two operations. inode_copy_up() should set the
label appropriately and inode_copy_up_xattr() should prevent the label set by
inode_copy_up() from being clobbered.

Note that inode_copy_up() has access to the lower file label and can perform
some sort of incantation to transmute it before applying it.

David
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Patch
diff mbox

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index ffa5a642629a..c5d893e2ff23 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3200,6 +3200,20 @@  static void selinux_inode_getsecid(const struct inode *inode, u32 *secid)
 	*secid = isec->sid;
 }
 
+static int selinux_inode_copy_up(struct dentry *src, struct dentry *dst)
+{
+	return 0;
+}
+
+static int selinux_inode_copy_up_xattr(struct dentry *src, struct dentry *dst,
+				       const char *name, void *value,
+				       size_t *size)
+{
+	if (strcmp(name, XATTR_NAME_SELINUX) == 0)
+		return 1; /* Discard */
+	return 0;
+}
+
 /* file security operations */
 
 static int selinux_revalidate_file_permission(struct file *file, int mask)
@@ -5917,6 +5931,8 @@  static struct security_operations selinux_ops = {
 	.inode_setsecurity =		selinux_inode_setsecurity,
 	.inode_listsecurity =		selinux_inode_listsecurity,
 	.inode_getsecid =		selinux_inode_getsecid,
+	.inode_copy_up =		selinux_inode_copy_up,
+	.inode_copy_up_xattr =		selinux_inode_copy_up_xattr,
 
 	.file_permission =		selinux_file_permission,
 	.file_alloc_security =		selinux_file_alloc_security,