Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759165AbZCSR4p (ORCPT ); Thu, 19 Mar 2009 13:56:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752022AbZCSR4g (ORCPT ); Thu, 19 Mar 2009 13:56:36 -0400 Received: from gateway-1237.mvista.com ([63.81.120.158]:42952 "EHLO gateway-1237.mvista.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751807AbZCSR4g (ORCPT ); Thu, 19 Mar 2009 13:56:36 -0400 Message-ID: <49C2874D.3080002@ct.jp.nec.com> Date: Thu, 19 Mar 2009 10:56:29 -0700 From: Hiroshi Shimamoto User-Agent: Thunderbird 2.0.0.21 (Windows/20090302) MIME-Version: 1.0 To: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org Subject: [PATCH] x86: signal: check signal stack overflow properly Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3177 Lines: 100 From: Hiroshi Shimamoto Impact: cleanup Check alternate signal stack overflow with proper stack pointer. The stack pointer of the next signal frame is different if that task has i387 state. On x86_64, redzone would be included. No need to check SA_ONSTACK if we're already using alternate signal stack. Signed-off-by: Hiroshi Shimamoto --- arch/x86/kernel/signal.c | 48 +++++++++++++++++++++++++-------------------- 1 files changed, 27 insertions(+), 21 deletions(-) diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 4da412a..62f2164 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -211,31 +211,27 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, { /* Default to using normal stack */ unsigned long sp = regs->sp; + int onsigstack = on_sig_stack(sp); #ifdef CONFIG_X86_64 /* redzone */ sp -= 128; #endif /* CONFIG_X86_64 */ - /* - * If we are on the alternate signal stack and would overflow it, don't. - * Return an always-bogus address instead so we will die with SIGSEGV. - */ - if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size))) - return (void __user *) -1L; - - /* This is the X/Open sanctioned signal stack switching. */ - if (ka->sa.sa_flags & SA_ONSTACK) { - if (sas_ss_flags(sp) == 0) - sp = current->sas_ss_sp + current->sas_ss_size; - } else { + if (!onsigstack) { + /* This is the X/Open sanctioned signal stack switching. */ + if (ka->sa.sa_flags & SA_ONSTACK) { + if (sas_ss_flags(sp) == 0) + sp = current->sas_ss_sp + current->sas_ss_size; + } else { #ifdef CONFIG_X86_32 - /* This is the legacy signal stack switching. */ - if ((regs->ss & 0xffff) != __USER_DS && - !(ka->sa.sa_flags & SA_RESTORER) && - ka->sa.sa_restorer) - sp = (unsigned long) ka->sa.sa_restorer; + /* This is the legacy signal stack switching. */ + if ((regs->ss & 0xffff) != __USER_DS && + !(ka->sa.sa_flags & SA_RESTORER) && + ka->sa.sa_restorer) + sp = (unsigned long) ka->sa.sa_restorer; #endif /* CONFIG_X86_32 */ + } } if (used_math()) { @@ -244,12 +240,22 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, sp = round_down(sp, 64); #endif /* CONFIG_X86_64 */ *fpstate = (void __user *)sp; - - if (save_i387_xstate(*fpstate) < 0) - return (void __user *)-1L; } - return (void __user *)align_sigframe(sp - frame_size); + sp = align_sigframe(sp - frame_size); + + /* + * If we are on the alternate signal stack and would overflow it, don't. + * Return an always-bogus address instead so we will die with SIGSEGV. + */ + if (onsigstack && !likely(on_sig_stack(sp))) + return (void __user *)-1L; + + /* save i387 state */ + if (used_math() && save_i387_xstate(*fpstate) < 0) + return (void __user *)-1L; + + return (void __user *)sp; } #ifdef CONFIG_X86_32 -- 1.6.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/