[PATCH] fs: Reorder inode_owner_or_capable() to avoid needless

[PATCH] fs: Reorder inode_owner_or_capable() to avoid needless

[Kees Cook]

Checking for capabilities should be the last operation when performing
access control tests so that PF_SUPERPRIV is set only when it was required
for success (implying that the capability was needed for the operation).

Reported-by: Solar Designer <solar@openwall.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/inode.c | 2 +-
 fs/namei.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index db5914783a71..7092debe90cc 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2023,7 +2023,7 @@ bool inode_owner_or_capable(const struct inode *inode)
 		return true;
 
 	ns = current_user_ns();
-	if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid))
+	if (kuid_has_mapping(ns, inode->i_uid) && ns_capable(ns, CAP_FOWNER))
 		return true;
 	return false;
 }
diff --git a/fs/namei.c b/fs/namei.c
index 6571a5f5112e..efe53a5d0737 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1008,7 +1008,7 @@ static int may_linkat(struct path *link)
 	/* Source inode owner (or CAP_FOWNER) can hardlink all they like,
 	 * otherwise, it must be a safe source.
 	 */
-	if (inode_owner_or_capable(inode) || safe_hardlink_source(inode))
+	if (safe_hardlink_source(inode) || inode_owner_or_capable(inode))
 		return 0;
 
 	audit_log_link_denied("linkat", link);
-- 
2.7.4


-- 
Kees Cook
Pixel Security

Re: [PATCH] fs: Reorder inode_owner_or_capable() to avoid needless

[Serge E. Hallyn]

Quoting Kees Cook (keescook@chromium.org):
> Checking for capabilities should be the last operation when performing
> access control tests so that PF_SUPERPRIV is set only when it was required
> for success (implying that the capability was needed for the operation).
> 
> Reported-by: Solar Designer <solar@openwall.com>
> Cc: Serge E. Hallyn <serge@hallyn.com>

Makes sense, thanks.

Acked-by: Serge Hallyn <serge@hallyn.com>

> Cc: Andy Lutomirski <luto@kernel.org>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  fs/inode.c | 2 +-
>  fs/namei.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index db5914783a71..7092debe90cc 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -2023,7 +2023,7 @@ bool inode_owner_or_capable(const struct inode *inode)
>  		return true;
>  
>  	ns = current_user_ns();
> -	if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid))
> +	if (kuid_has_mapping(ns, inode->i_uid) && ns_capable(ns, CAP_FOWNER))
>  		return true;
>  	return false;
>  }
> diff --git a/fs/namei.c b/fs/namei.c
> index 6571a5f5112e..efe53a5d0737 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -1008,7 +1008,7 @@ static int may_linkat(struct path *link)
>  	/* Source inode owner (or CAP_FOWNER) can hardlink all they like,
>  	 * otherwise, it must be a safe source.
>  	 */
> -	if (inode_owner_or_capable(inode) || safe_hardlink_source(inode))
> +	if (safe_hardlink_source(inode) || inode_owner_or_capable(inode))
>  		return 0;
>  
>  	audit_log_link_denied("linkat", link);
> -- 
> 2.7.4
> 
> 
> -- 
> Kees Cook
> Pixel Security

Re: [PATCH] fs: Reorder inode_owner_or_capable() to avoid needless

[Andy Lutomirski]

On Tue, Jun 20, 2017 at 2:40 PM, Kees Cook <keescook@chromium.org> wrote:
> Checking for capabilities should be the last operation when performing
> access control tests so that PF_SUPERPRIV is set only when it was required
> for success (implying that the capability was needed for the operation).
>

Reviewed-by: Andy Lutomirski <luto@kernel.org>

Re: [PATCH] fs: Reorder inode_owner_or_capable() to avoid needless

[Al Viro]

On Tue, Jun 20, 2017 at 02:40:24PM -0700, Kees Cook wrote:
> Checking for capabilities should be the last operation when performing
> access control tests so that PF_SUPERPRIV is set only when it was required
> for success (implying that the capability was needed for the operation).

Applied