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[PATCH 4/9] selinux: Implementation for inode_copy_up_xattr() hook

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  [PATCH 4/9] selinux: Implementation for inode_copy_up_xattr() hook Vivek Goyal <vgoyal@redhat.com> - 2016-07-13 16:50 +0200
    Re: [PATCH 4/9] selinux: Implementation for inode_copy_up_xattr()  hook Stephen Smalley <sds@tycho.nsa.gov> - 2016-07-13 17:00 +0200

#1442511 — [PATCH 4/9] selinux: Implementation for inode_copy_up_xattr() hook

When a file is copied up in overlay, we have already created file on upper/
with right label and there is no need to copy up selinux label/xattr from
lower file to upper file. In fact in case of context mount, we don't want
to copy up label as newly created file got its label from context= option.

Signed-off-by: Vivek Goyal <vgoyal@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 c82ee54..4fda548 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3290,6 +3290,21 @@ static int selinux_inode_copy_up(struct dentry *src, struct cred **new)
 	return 0;
 }
 
+static int selinux_inode_copy_up_xattr(const char *name)
+{
+	/* The copy_up hook above sets the initial context on an inode, but we
+	 * don't then want to overwrite it by blindly copying all the lower
+	 * xattrs up.  Instead, we have to filter out SELinux-related xattrs.
+	 */
+	if (strcmp(name, XATTR_NAME_SELINUX) == 0)
+		return 1; /* Discard */
+	/*
+	 * Any other attribute apart from SELINUX is not claimed, supported
+	 * by selinux.
+	 */
+	return -EOPNOTSUPP;
+}
+
 /* file security operations */
 
 static int selinux_revalidate_file_permission(struct file *file, int mask)
@@ -6077,6 +6092,7 @@ static struct security_hook_list selinux_hooks[] = {
 	LSM_HOOK_INIT(inode_listsecurity, selinux_inode_listsecurity),
 	LSM_HOOK_INIT(inode_getsecid, selinux_inode_getsecid),
 	LSM_HOOK_INIT(inode_copy_up, selinux_inode_copy_up),
+	LSM_HOOK_INIT(inode_copy_up_xattr, selinux_inode_copy_up_xattr),
 
 	LSM_HOOK_INIT(file_permission, selinux_file_permission),
 	LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
-- 
2.7.4

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#1442524 — Re: [PATCH 4/9] selinux: Implementation for inode_copy_up_xattr() hook

On 07/13/2016 10:44 AM, Vivek Goyal wrote:
> When a file is copied up in overlay, we have already created file on upper/
> with right label and there is no need to copy up selinux label/xattr from
> lower file to upper file. In fact in case of context mount, we don't want
> to copy up label as newly created file got its label from context= option.
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Acked-by: Stephen Smalley <sds@tycho.nsa.gov>

> ---
>  security/selinux/hooks.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index c82ee54..4fda548 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3290,6 +3290,21 @@ static int selinux_inode_copy_up(struct dentry *src, struct cred **new)
>  	return 0;
>  }
>  
> +static int selinux_inode_copy_up_xattr(const char *name)
> +{
> +	/* The copy_up hook above sets the initial context on an inode, but we
> +	 * don't then want to overwrite it by blindly copying all the lower
> +	 * xattrs up.  Instead, we have to filter out SELinux-related xattrs.
> +	 */
> +	if (strcmp(name, XATTR_NAME_SELINUX) == 0)
> +		return 1; /* Discard */
> +	/*
> +	 * Any other attribute apart from SELINUX is not claimed, supported
> +	 * by selinux.
> +	 */
> +	return -EOPNOTSUPP;
> +}
> +
>  /* file security operations */
>  
>  static int selinux_revalidate_file_permission(struct file *file, int mask)
> @@ -6077,6 +6092,7 @@ static struct security_hook_list selinux_hooks[] = {
>  	LSM_HOOK_INIT(inode_listsecurity, selinux_inode_listsecurity),
>  	LSM_HOOK_INIT(inode_getsecid, selinux_inode_getsecid),
>  	LSM_HOOK_INIT(inode_copy_up, selinux_inode_copy_up),
> +	LSM_HOOK_INIT(inode_copy_up_xattr, selinux_inode_copy_up_xattr),
>  
>  	LSM_HOOK_INIT(file_permission, selinux_file_permission),
>  	LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
> 

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