From: Eric Sandeen <sandeen@redhat.com>
Date: Tue, 8 Jul 2008 15:07:17 -0500
Subject: [fs] introduce is_owner_or_cap
Message-id: 4873C8F5.2060302@redhat.com
O-Subject: [PATCH RHEL5 3/9] is_owner_or_cap
Bugzilla: 443896
RH-Acked-by: Jeff Moyer <jmoyer@redhat.com>
RH-Acked-by: Jeff Layton <jlayton@redhat.com>
RH-Acked-by: Alexander Viro <aviro@redhat.com>

This is for:

Bugzilla Bug 443896: RFE: [Ext4 enabler] backport vfs
helpers to facilitate ext4 backport and testing

From: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Date: Tue, 17 Jul 2007 09:30:08 +0000 (+0530)
Subject: Introduce is_owner_or_cap() to wrap CAP_FOWNER use with fsuid check
X-Git-Tag: v2.6.23-rc1~519
X-Git-Url: http://git.engineering.redhat.com/?p=linux-2.6.git;a=commitdiff_plain;h=3bd858ab1c451725c07a805dcb315215dc85b86e

Introduce is_owner_or_cap() to wrap CAP_FOWNER use with fsuid check

Introduce is_owner_or_cap() macro in fs.h, and convert over relevant
users to it. This is done because we want to avoid bugs in the future
where we check for only effective fsuid of the current task against a
file's owning uid, without simultaneously checking for CAP_FOWNER as
well, thus violating its semantics.
[ XFS uses special macros and structures, and in general looked ...
untouchable, so we leave it alone -- but it has been looked over. ]

The (current->fsuid != inode->i_uid) check in generic_permission() and
exec_permission_lite() is left alone, because those operations are
covered by CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH. Similarly operations
falling under the purview of CAP_CHOWN and CAP_LEASE are also left alone.

Signed-off-by: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Cc: Al Viro <viro@ftp.linux.org.uk>
Acked-by: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 28c201f..fd80f94 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -993,6 +993,9 @@ static inline void unlock_super(struct super_block * sb)
 	mutex_unlock(&sb->s_lock);
 }
 
+#define is_owner_or_cap(inode)  \
+	((current->fsuid == (inode)->i_uid) || capable(CAP_FOWNER))
+
 /*
  * VFS helper functions..
  */