[GFS2] don't call permission()

GFS2 calls permission() to verify permissions after locks on the files
have been taken.

For this it's sufficient to call gfs2_permission() instead.  This
results in the following changes:

  - IS_RDONLY() check is not performed
  - IS_IMMUTABLE() check is not performed
  - devcgroup_inode_permission() is not called
  - security_inode_permission() is not called

IS_RDONLY() should be unnecessary anyway, as the per-mount read-only
flag should provide protection against read-only remounts during
operations.  do_gfs2_set_flags() has been fixed to perform
mnt_want_write()/mnt_drop_write() to protect against remounting
read-only.

IS_IMMUTABLE has been added to gfs2_permission()

Repeating the security checks seems to be pointless, as they don't
normally change, and if they do, it's independent of the filesystem
state.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/fs/gfs2/ops_file.c b/fs/gfs2/ops_file.c
index 0ff512a11925..1737af98a420 100644
--- a/fs/gfs2/ops_file.c
+++ b/fs/gfs2/ops_file.c
@@ -15,6 +15,7 @@
 #include <linux/uio.h>
 #include <linux/blkdev.h>
 #include <linux/mm.h>
+#include <linux/mount.h>
 #include <linux/fs.h>
 #include <linux/gfs2_ondisk.h>
 #include <linux/ext2_fs.h>
@@ -220,10 +221,14 @@ static int do_gfs2_set_flags(struct file *filp, u32 reqflags, u32 mask)
         int error;
         u32 new_flags, flags;
 
-        error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
+        error = mnt_want_write(filp->f_path.mnt);
         if (error)
                 return error;
 
+        error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
+        if (error)
+                goto out_drop_write;
+
         flags = ip->i_di.di_flags;
         new_flags = (flags & ~mask) | (reqflags & mask);
         if ((new_flags ^ flags) == 0)
@@ -242,7 +247,7 @@ static int do_gfs2_set_flags(struct file *filp, u32 reqflags, u32 mask)
             !capable(CAP_LINUX_IMMUTABLE))
                 goto out;
         if (!IS_IMMUTABLE(inode)) {
-                error = permission(inode, MAY_WRITE, NULL);
+                error = gfs2_permission(inode, MAY_WRITE);
                 if (error)
                         goto out;
         }
@@ -272,6 +277,8 @@ out_trans_end:
         gfs2_trans_end(sdp);
 out:
         gfs2_glock_dq_uninit(&gh);
+out_drop_write:
+        mnt_drop_write(filp->f_path.mnt);
         return error;
 }