[PATCH] xfs: fix sgid inheritance for subdirectories inheriting default acls [V2]

[Carlos Maiolino <cmaiolino@xxxxxxxxxx>]

XFS removes sgid bits of subdirectories under a directory containing a default
acl.

When a default acl is set, it implies xfs to call xfs_setattr_nonsize() in its
code path. Such function is shared among mkdir and chmod system calls, and
does some checks unneeded by mkdir (calling inode_change_ok()). Such checks
remove sgid bit from the inode after it has been granted.

With this patch, we extend the meaning of XFS_ATTR_NOACL flag to avoid these
checks when acls are being inherited (thanks hch).

Also, xfs_setattr_mode, doesn't need to re-check for group id and capabilities
permissions, this only implies in another try to remove sgid bit from the
directories. Such check is already done either on inode_change_ok() or
xfs_setattr_nonsize().

Changelog:

V2: Extends the meaning of XFS_ATTR_NOACL instead of wrap the tests into another
    function

Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
---
 fs/xfs/xfs_iops.c |   27 ++++++++++++++-------------
 1 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index ca9ecaa..3547d89 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -467,9 +467,6 @@ xfs_setattr_mode(
        ASSERT(tp);
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
 
-       if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
-               mode &= ~S_ISGID;
-
        ip->i_d.di_mode &= S_IFMT;
        ip->i_d.di_mode |= mode & ~S_IFMT;
 
@@ -495,15 +492,18 @@ xfs_setattr_nonsize(
 
        trace_xfs_setattr(ip);
 
-       if (mp->m_flags & XFS_MOUNT_RDONLY)
-               return XFS_ERROR(EROFS);
+       /* If acls are being inherited, we already have this checked */
+       if (!(flags & XFS_ATTR_NOACL)) {
+               if (mp->m_flags & XFS_MOUNT_RDONLY)
+                       return XFS_ERROR(EROFS);
 
-       if (XFS_FORCED_SHUTDOWN(mp))
-               return XFS_ERROR(EIO);
+               if (XFS_FORCED_SHUTDOWN(mp))
+                       return XFS_ERROR(EIO);
 
-       error = -inode_change_ok(inode, iattr);
-       if (error)
-               return XFS_ERROR(error);
+               error = -inode_change_ok(inode, iattr);
+               if (error)
+                       return XFS_ERROR(error);
+       }
 
        ASSERT((mask & ATTR_SIZE) == 0);
 
@@ -594,9 +594,10 @@ xfs_setattr_nonsize(
                 * The set-user-ID and set-group-ID bits of a file will be
                 * cleared upon successful return from chown()
                 */
-               if ((ip->i_d.di_mode & (S_ISUID|S_ISGID)) &&
-                   !capable(CAP_FSETID))
-                       ip->i_d.di_mode &= ~(S_ISUID|S_ISGID);
+               if (!S_ISDIR(inode->i_mode))
+                       if ((ip->i_d.di_mode & (S_ISUID|S_ISGID)) &&
+                           !capable(CAP_FSETID))
+                               ip->i_d.di_mode &= ~(S_ISUID|S_ISGID);
 
                /*
                 * Change the ownerships and register quota modifications
-- 
1.7.1