From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752031AbcGRVql (ORCPT ); Mon, 18 Jul 2016 17:46:41 -0400 Received: from mail.kernel.org ([198.145.29.136]:38854 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751370AbcGRVqj (ORCPT ); Mon, 18 Jul 2016 17:46:39 -0400 From: Andy Lutomirski To: x86@kernel.org Cc: Borislav Petkov , linux-kernel@vger.kernel.org, Andy Lutomirski Subject: [PATCH] x86/vdso: Error out if the vDSO isn't a valid DSO Date: Mon, 18 Jul 2016 14:46:35 -0700 Message-Id: <8a30e0a07c3b47ff917a8daa2df5e407cc0c6698.1468878336.git.luto@kernel.org> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Some distros has been playing with toolchain changes that can affect the type of ELF objects built. Occasionally, this goes wrong and the vDSO ends up not being a DSO at all. This causes the kernel to end up broken in a surprisingly subtle way -- glibc apparently silently ignores a vDSO that isn't a DSO, so everything works, albeit slowly, until users try a different libc implementation. Make the kernel build process a bit more robust: fail outright if the vDSO isn't ET_DYN or is missing its PT_DYNAMIC segment. I've never seen this in an unmodified kernel. See https://github.com/docker/docker/issues/23378 Signed-off-by: Andy Lutomirski --- arch/x86/entry/vdso/vdso2c.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/entry/vdso/vdso2c.h b/arch/x86/entry/vdso/vdso2c.h index 63a03bb91497..4f741192846d 100644 --- a/arch/x86/entry/vdso/vdso2c.h +++ b/arch/x86/entry/vdso/vdso2c.h @@ -22,6 +22,9 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len, ELF(Phdr) *pt = (ELF(Phdr) *)(raw_addr + GET_LE(&hdr->e_phoff)); + if (hdr->e_type != ET_DYN) + fail("input is not a shared object\n"); + /* Walk the segment table. */ for (i = 0; i < GET_LE(&hdr->e_phnum); i++) { if (GET_LE(&pt[i].p_type) == PT_LOAD) { @@ -49,6 +52,9 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len, if (stripped_len < load_size) fail("stripped input is too short\n"); + if (!dyn) + fail("input has no PT_DYNAMIC section -- your toolchain is buggy\n"); + /* Walk the dynamic table */ for (i = 0; dyn + i < dyn_end && GET_LE(&dyn[i].d_tag) != DT_NULL; i++) { -- 2.7.4