From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xjnr62W0jzDqGX for ; Fri, 1 Sep 2017 02:28:54 +1000 (AEST) Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v7VGPAK2125630 for ; Thu, 31 Aug 2017 12:28:52 -0400 Received: from e23smtp06.au.ibm.com (e23smtp06.au.ibm.com [202.81.31.148]) by mx0a-001b2d01.pphosted.com with ESMTP id 2cphwwyhvm-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 31 Aug 2017 12:28:51 -0400 Received: from localhost by e23smtp06.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 1 Sep 2017 02:28:49 +1000 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay06.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v7VGSkj438666468 for ; Fri, 1 Sep 2017 02:28:46 +1000 Received: from d23av01.au.ibm.com (localhost [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v7VGSkVf018713 for ; Fri, 1 Sep 2017 02:28:46 +1000 From: "Naveen N. Rao" To: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, Anton Blanchard , Srikar Dronamraju , Richard Weinberger Subject: [PATCH] powerpc/signal: Properly handle return value from uprobe_deny_signal() Date: Thu, 31 Aug 2017 21:55:57 +0530 Message-Id: <20170831162557.24904-1-naveen.n.rao@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , When a uprobe is installed on an instruction that we currently do not emulate, we copy the instruction into a xol buffer and single step that instruction. If that instruction generates a fault, we abort the single stepping before invoking the signal handler. Once the signal handler is done, the uprobe trap is hit again since the instruction is retried and the process repeats. We use uprobe_deny_signal() to detect if the xol instruction triggered a signal. If so, we clear TIF_SIGPENDING and set TIF_UPROBE so that the signal is not handled until after the single stepping is aborted. In this case, uprobe_deny_signal() returns true and get_signal() ends up returning 0. However, in do_signal(), we are not looking at the return value, but depending on ksig.sig for further action, all with an uninitialized ksig that is not touched in this scenario. Fix the same by initializing ksig.sig to 0. Fixes: 129b69df9c907 ("powerpc: Use get_signal() signal_setup_done()") Reported-by: Anton Blanchard Signed-off-by: Naveen N. Rao --- arch/powerpc/kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c index e9436c5e1e09..3d7539b90010 100644 --- a/arch/powerpc/kernel/signal.c +++ b/arch/powerpc/kernel/signal.c @@ -103,7 +103,7 @@ static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka, static void do_signal(struct task_struct *tsk) { sigset_t *oldset = sigmask_to_save(); - struct ksignal ksig; + struct ksignal ksig = { .sig = 0 }; int ret; int is32 = is_32bit_task(); -- 2.14.1