tmpfs: clear S_ISGID when setting posix ACLs

commit 497de07d89c1410d76a15bec2bb41f24a2a89f31 upstream.

This change was missed the tmpfs modification in In CVE-2016-7097
commit 073931017b49 ("posix_acl: Clear SGID bit when setting
file permissions")
It can test by xfstest generic/375, which failed to clear
setgid bit in the following test case on tmpfs:

  touch $testfile
  chown 100:100 $testfile
  chmod 2755 $testfile
  _runas -u 100 -g 101 -- setfacl -m u::rwx,g::rwx,o::rwx $testfile

Signed-off-by: Gu Zheng <guzheng1@huawei.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/fs/generic_acl.c b/fs/generic_acl.c
index b3f3676796d31a6870a771ed6952977cfc16d448..7855cfb938f6aecf9a74ee34499749c78e0328ec 100644 (file)
--- a/fs/generic_acl.c
+++ b/fs/generic_acl.c
@@ -82,19 +82,21 @@ generic_acl_set(struct dentry *dentry, const char *name, const void *value,
                        return PTR_ERR(acl);
        }
        if (acl) {
+               struct posix_acl *old_acl;
+
                error = posix_acl_valid(acl);
                if (error)
                        goto failed;
                switch (type) {
                case ACL_TYPE_ACCESS:
-                       error = posix_acl_equiv_mode(acl, &inode->i_mode);
+                       old_acl = acl;
+                       error = posix_acl_update_mode(inode, &inode->i_mode,
+                                                     &acl);
                        if (error < 0)
                                goto failed;
+                       if (!acl)
+                               posix_acl_release(old_acl);
                        inode->i_ctime = CURRENT_TIME;
-                       if (error == 0) {
-                               posix_acl_release(acl);
-                               acl = NULL;
-                       }
                        break;
                case ACL_TYPE_DEFAULT:
                        if (!S_ISDIR(inode->i_mode)) {