From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753985AbaHTMBt (ORCPT ); Wed, 20 Aug 2014 08:01:49 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:58950 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752553AbaHTLoK (ORCPT ); Wed, 20 Aug 2014 07:44:10 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, "David S. Miller" , Jiri Slaby Subject: [PATCH 3.12 050/104] sparc64: Don't bark so loudly about 32-bit tasks generating 64-bit fault addresses. Date: Wed, 20 Aug 2014 13:43:13 +0200 Message-Id: X-Mailer: git-send-email 2.0.4 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "David S. Miller" 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ Upstream commit e5c460f46ae7ee94831cb55cb980f942aa9e5a85 ] This was found using Dave Jone's trinity tool. When a user process which is 32-bit performs a load or a store, the cpu chops off the top 32-bits of the effective address before translating it. This is because we run 32-bit tasks with the PSTATE_AM (address masking) bit set. We can't run the kernel with that bit set, so when the kernel accesses userspace no address masking occurs. Since a 32-bit process will have no mappings in that region we will properly fault, so we don't try to handle this using access_ok(), which can safely just be a NOP on sparc64. Real faults from 32-bit processes should never generate such addresses so a bug check was added long ago, and it barks in the logs if this happens. But it also barks when a kernel user access causes this condition, and that _can_ happen. For example, if a pointer passed into a system call is "0xfffffffc" and the kernel access 4 bytes offset from that pointer. Just handle such faults normally via the exception entries. Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby --- arch/sparc/mm/fault_64.c | 16 +--------------- 1 file changed, 1 insertion(+), 15 deletions(-) diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c index a99d0da04850..3841a081beb3 100644 --- a/arch/sparc/mm/fault_64.c +++ b/arch/sparc/mm/fault_64.c @@ -280,18 +280,6 @@ static void noinline __kprobes bogus_32bit_fault_tpc(struct pt_regs *regs) show_regs(regs); } -static void noinline __kprobes bogus_32bit_fault_address(struct pt_regs *regs, - unsigned long addr) -{ - static int times; - - if (times++ < 10) - printk(KERN_ERR "FAULT[%s:%d]: 32-bit process " - "reports 64-bit fault address [%lx]\n", - current->comm, current->pid, addr); - show_regs(regs); -} - asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs) { struct mm_struct *mm = current->mm; @@ -320,10 +308,8 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs) goto intr_or_no_mm; } } - if (unlikely((address >> 32) != 0)) { - bogus_32bit_fault_address(regs, address); + if (unlikely((address >> 32) != 0)) goto intr_or_no_mm; - } } if (regs->tstate & TSTATE_PRIV) { -- 2.0.4