[PATCH 2/2] posix_acl: Clear SGID bit when modifying file permissions

[Jan Kara <jack@suse.cz>]

When file permissions are modified via chmod(2) and the user modifying the
permissions is not capable of setting SGID bit for the file, the bit gets
cleared in inode_change_ok(). However this is not the case when file
permissions get modified via setfacl(1). Add clearing of SGID bit to
posix_acl_equiv_mode().

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/posix_acl.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 0a7c5119ed8d..d714b9216418 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -311,8 +311,12 @@ posix_acl_equiv_mode(struct inode *inode, const struct posix_acl *acl,
 				return -EINVAL;
 		}
 	}
-        if (mode_p)
+        if (mode_p) {
+		if (!in_group_p(inode->i_gid) &&
+		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
+			*mode_p &= ~S_ISGID;
                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
+	}
         return not_equiv;
 }
 EXPORT_SYMBOL(posix_acl_equiv_mode);
-- 
2.6.6