CRED: Introduce credential access wrappers

The patches that are intended to introduce copy-on-write credentials for 2.6.28
require abstraction of access to some fields of the task structure,
particularly for the case of one task accessing another's credentials where RCU
will have to be observed.

Introduced here are trivial no-op versions of the desired accessors for current
and other tasks so that other subsystems can start to be converted over more
easily.

Wrappers are introduced into a new header (linux/cred.h) for UID/GID,
EUID/EGID, SUID/SGID, FSUID/FSGID, cap_effective and current's subscribed
user_struct.  These wrappers are macros because the ordering between header
files mitigates against making them inline functions.

linux/cred.h is #included from linux/sched.h.

Further, XFS is modified such that it no longer defines and uses parameterised
versions of current_fs[ug]id(), thus getting rid of the namespace collision
otherwise incurred.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

3 files changed, 6 insertions, 8 deletions

diff --git a/fs/xfs/linux-2.6/xfs_linux.h b/fs/xfs/linux-2.6/xfs_linux.h
index 3b7c4ff48ba0..cc0f7b3a9795 100644
--- a/fs/xfs/linux-2.6/xfs_linux.h
+++ b/fs/xfs/linux-2.6/xfs_linux.h
@@ -126,8 +126,6 @@
 
 #define current_cpu()           (raw_smp_processor_id())
 #define current_pid()           (current->pid)
-#define current_fsuid(cred)     (current->fsuid)
-#define current_fsgid(cred)     (current->fsgid)
 #define current_test_flags(f)   (current->flags & (f))
 #define current_set_flags_nested(sp, f)         \
                 (*(sp) = current->flags, current->flags |= (f))
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 358511b85ced..00e80df9dd9d 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1081,8 +1081,8 @@ xfs_ialloc(
         ip->i_d.di_onlink = 0;
         ip->i_d.di_nlink = nlink;
         ASSERT(ip->i_d.di_nlink == nlink);
-        ip->i_d.di_uid = current_fsuid(cr);
-        ip->i_d.di_gid = current_fsgid(cr);
+        ip->i_d.di_uid = current_fsuid();
+        ip->i_d.di_gid = current_fsgid();
         ip->i_d.di_projid = prid;
         memset(&(ip->i_d.di_pad[0]), 0, sizeof(ip->i_d.di_pad));
 
diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 588bb4aa215d..aa238c8fbd7a 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -182,7 +182,7 @@ xfs_setattr(
         xfs_ilock(ip, lock_flags);
 
         /* boolean: are we the file owner? */
-        file_owner = (current_fsuid(credp) == ip->i_d.di_uid);
+        file_owner = (current_fsuid() == ip->i_d.di_uid);
 
         /*
          * Change various properties of a file.
@@ -1533,7 +1533,7 @@ xfs_create(
          * Make sure that we have allocated dquot(s) on disk.
          */
         error = XFS_QM_DQVOPALLOC(mp, dp,
-                        current_fsuid(credp), current_fsgid(credp), prid,
+                        current_fsuid(), current_fsgid(), prid,
                         XFS_QMOPT_QUOTALL|XFS_QMOPT_INHERIT, &udqp, &gdqp);
         if (error)
                 goto std_return;
@@ -2269,7 +2269,7 @@ xfs_mkdir(
          * Make sure that we have allocated dquot(s) on disk.
          */
         error = XFS_QM_DQVOPALLOC(mp, dp,
-                        current_fsuid(credp), current_fsgid(credp), prid,
+                        current_fsuid(), current_fsgid(), prid,
                         XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT, &udqp, &gdqp);
         if (error)
                 goto std_return;
@@ -2495,7 +2495,7 @@ xfs_symlink(
          * Make sure that we have allocated dquot(s) on disk.
          */
         error = XFS_QM_DQVOPALLOC(mp, dp,
-                        current_fsuid(credp), current_fsgid(credp), prid,
+                        current_fsuid(), current_fsgid(), prid,
                         XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT, &udqp, &gdqp);
         if (error)
                 goto std_return;