cifs: fix a memleak with modefromsid

kmemleak reported a memory leak allocated in query_info() when cifs is
working with modefromsid.

  backtrace:
    [<00000000aeef6a1e>] slab_post_alloc_hook+0x58/0x510
    [<00000000b2f7a440>] __kmalloc+0x1a0/0x390
    [<000000006d470ebc>] query_info+0x5b5/0x700 [cifs]
    [<00000000bad76ce0>] SMB2_query_acl+0x2b/0x30 [cifs]
    [<000000001fa09606>] get_smb2_acl_by_path+0x2f3/0x720 [cifs]
    [<000000001b6ebab7>] get_smb2_acl+0x75/0x90 [cifs]
    [<00000000abf43904>] cifs_acl_to_fattr+0x13b/0x1d0 [cifs]
    [<00000000a5372ec3>] cifs_get_inode_info+0x4cd/0x9a0 [cifs]
    [<00000000388e0a04>] cifs_revalidate_dentry_attr+0x1cd/0x510 [cifs]
    [<0000000046b6b352>] cifs_getattr+0x8a/0x260 [cifs]
    [<000000007692c95e>] vfs_getattr_nosec+0xa1/0xc0
    [<00000000cbc7d742>] vfs_getattr+0x36/0x40
    [<00000000de8acf67>] vfs_statx_fd+0x4a/0x80
    [<00000000a58c6adb>] __do_sys_newfstat+0x31/0x70
    [<00000000300b3b4e>] __x64_sys_newfstat+0x16/0x20
    [<000000006d8e9c48>] do_syscall_64+0x37/0x80

This patch add missing kfree for pntsd when mounting modefromsid option.

Cc: Stable <stable@vger.kernel.org> # v5.4+
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsacl.c

@@ -1266,6 +1266,7 @@ cifs_acl_to_fattr(struct cifs_sb_info *cifs_sb, struct cifs_fattr *fattr,
  cifs_dbg(VFS, "%s: error %d getting sec desc\n", __func__, rc);
  } else if (mode_from_special_sid) {
  rc = parse_sec_desc(cifs_sb, pntsd, acllen, fattr, true);
+ kfree(pntsd);
  } else {
  /* get approximated mode from ACL */
  rc = parse_sec_desc(cifs_sb, pntsd, acllen, fattr, false);