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Message-ID: <20170621165306.GA48013@beast>
Date: Wed, 21 Jun 2017 09:53:06 -0700
From: Kees Cook <keescook@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
linux-fsdevel@...r.kernel.org, Solar Designer <solar@...nwall.com>,
Serge Hallyn <serge@...lyn.com>,
Andy Lutomirski <luto@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH v2] fs: Reorder inode_owner_or_capable() to avoid needless
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@...nwall.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Acked-by: Serge Hallyn <serge@...lyn.com>
Reviewed-by: Andy Lutomirski <luto@...nel.org>
---
v2: add acks/reviews, actually include akpm in "To" :)
---
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
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