From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vineet Gupta Subject: [PATCH 2/2] ARC: [Review] Prevent incorrect syscall restarts Date: Fri, 28 Dec 2012 18:12:37 +0530 Message-ID: <1356698557-9000-2-git-send-email-vgupta@synopsys.com> References: <50DD91C1.3000809@synopsys.com> <1356698557-9000-1-git-send-email-vgupta@synopsys.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from alvesta.synopsys.com ([198.182.60.77]:50906 "EHLO alvesta.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751318Ab2L1MnI (ORCPT ); Fri, 28 Dec 2012 07:43:08 -0500 In-Reply-To: <1356698557-9000-1-git-send-email-vgupta@synopsys.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: viro@ZenIV.linux.org.uk Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Vineet Gupta Per Al Viro's "signals for dummies" https://lkml.org/lkml/2012/12/6/366 there are 3 golden rules for (not) restarting syscalls: " What we need to guarantee is * restarts do not happen on signals caught in interrupts or exceptions * restarts do not happen on signals caught in sigreturn() * restart should happen only once, even if we get through do_signal() many times." ARC Port already handled #1, this patch fixes #2 and #3. We use the additional state in pt_regs->orig_r8 to ckh if restarting has already been done once. Thanks to Al Viro for spotting this. Signed-off-by: Vineet Gupta --- arch/arc/include/asm/ptrace.h | 3 +++ arch/arc/kernel/signal.c | 12 ++++++++---- 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h index 7daa3a6..caf216e 100644 --- a/arch/arc/include/asm/ptrace.h +++ b/arch/arc/include/asm/ptrace.h @@ -93,6 +93,9 @@ struct user_regs_struct { #define in_syscall(regs) (regs->orig_r8 & orig_r8_IS_SCALL) #define in_brkpt_trap(regs) (regs->orig_r8 & orig_r8_IS_BRKPT) +#define syscall_wont_restart(regs) (regs->orig_r8 |= orig_r8_IS_SCALL_RESTARTED) +#define syscall_restartable(regs) !(regs->orig_r8 & orig_r8_IS_SCALL_RESTARTED) + #define current_pt_regs() \ ({ \ /* open-coded current_thread_info() */ \ diff --git a/arch/arc/kernel/signal.c b/arch/arc/kernel/signal.c index 464af3f..6671968 100644 --- a/arch/arc/kernel/signal.c +++ b/arch/arc/kernel/signal.c @@ -137,6 +137,9 @@ SYSCALL_DEFINE0(rt_sigreturn) if (do_sigaltstack(&sf->uc.uc_stack, NULL, regs->sp) == -EFAULT) goto badframe; + /* Don't restart from sigreturn */ + syscall_wont_restart(regs); + return regs->r0; badframe: @@ -331,13 +334,13 @@ void do_signal(struct pt_regs *regs) signr = get_signal_to_deliver(&info, &ka, regs, NULL); - /* Are we from a system call? */ - restart_scall = in_syscall(regs); + restart_scall = in_syscall(regs) && syscall_restartable(regs); if (signr > 0) { - if (restart_scall) + if (restart_scall) { arc_restart_syscall(&ka, regs); - + syscall_wont_restart(regs); /* No more restarts */ + } handle_signal(signr, &ka, &info, regs); return; } @@ -352,6 +355,7 @@ void do_signal(struct pt_regs *regs) regs->r8 = __NR_restart_syscall; regs->ret -= 4; } + syscall_wont_restart(regs); /* No more restarts */ } /* If there's no signal to deliver, restore the saved sigmask back */ -- 1.7.4.1