From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965097AbbA1EYV (ORCPT ); Tue, 27 Jan 2015 23:24:21 -0500 Received: from mail.kernel.org ([198.145.29.136]:40550 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965059AbbA1EYH (ORCPT ); Tue, 27 Jan 2015 23:24:07 -0500 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Anton Blanchard , Michael Ellerman , Zefan Li Subject: [PATCH 3.4 124/177] powerpc: do_notify_resume can be called with bad thread_info flags argument Date: Wed, 28 Jan 2015 12:09:42 +0800 Message-Id: <1422418236-12852-215-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1422418050-12581-1-git-send-email-lizf@kernel.org> References: <1422418050-12581-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Anton Blanchard 3.4.106-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 808be31426af57af22268ef0fcb42617beb3d15b upstream. Back in 7230c5644188 ("powerpc: Rework lazy-interrupt handling") we added a call out to restore_interrupts() (written in c) before calling do_notify_resume: bl restore_interrupts addi r3,r1,STACK_FRAME_OVERHEAD bl do_notify_resume Unfortunately do_notify_resume takes two arguments, the second one being the thread_info flags: void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags) We do populate r4 (the second argument) earlier, but restore_interrupts() is free to muck it up all it wants. My guess is the gcc compiler gods shone down on us and its register allocator never used r4. Sometimes, rarely, luck is on our side. LLVM on the other hand did trample r4. Signed-off-by: Anton Blanchard Signed-off-by: Michael Ellerman [lizf: Backported to 3.4: adjust context] Signed-off-by: Zefan Li --- arch/powerpc/kernel/entry_64.S | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index e500969..c3fc39e 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -813,7 +813,13 @@ user_work: b .ret_from_except_lite 1: bl .save_nvgprs + /* + * Use a non volatile GPR to save and restore our thread_info flags + * across the call to restore_interrupts. + */ + mr r30,r4 bl .restore_interrupts + mr r4,r30 addi r3,r1,STACK_FRAME_OVERHEAD bl .do_notify_resume b .ret_from_except -- 1.9.1