Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755645AbcDKPyb (ORCPT ); Mon, 11 Apr 2016 11:54:31 -0400 Received: from mga14.intel.com ([192.55.52.115]:27140 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755447AbcDKPy1 (ORCPT ); Mon, 11 Apr 2016 11:54:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,462,1455004800"; d="scan'208";a="83091616" Subject: [PATCH 3/8] x86, pkeys: make mprotect_key() mask off additional vm_flags To: linux-kernel@vger.kernel.org Cc: Dave Hansen , dave.hansen@linux.intel.com, linux-mm@kvack.org, x86@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org From: Dave Hansen Date: Mon, 11 Apr 2016 08:54:26 -0700 References: <20160411155422.A2B8FD0C@viggo.jf.intel.com> In-Reply-To: <20160411155422.A2B8FD0C@viggo.jf.intel.com> Message-Id: <20160411155426.EB4517DE@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3541 Lines: 94 From: Dave Hansen Today, mprotect() takes 4 bits of data: PROT_READ/WRITE/EXEC/NONE. Three of those bits: READ/WRITE/EXEC get translated directly in to vma->vm_flags by calc_vm_prot_bits(). If a bit is unset in mprotect()'s 'prot' argument then it must be cleared in vma->vm_flags during the mprotect() call. We do this clearing today by first calculating the VMA flags we want set, then clearing the ones we do not want to inherit from the original VMA: vm_flags = calc_vm_prot_bits(prot, key); ... newflags = vm_flags; newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); However, we *also* want to mask off the original VMA's vm_flags in which we store the protection key. To do that, this patch adds a new macro: ARCH_VM_PKEY_FLAGS which allows the architecture to specify additional bits that it would like cleared. We use that to ensure that the VM_PKEY_BIT* bits get cleared. Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner Cc: linux-mm@kvack.org Cc: x86@kernel.org Cc: torvalds@linux-foundation.org Cc: akpm@linux-foundation.org --- b/arch/x86/include/asm/pkeys.h | 2 ++ b/include/linux/pkeys.h | 1 + b/mm/mprotect.c | 11 ++++++++++- 3 files changed, 13 insertions(+), 1 deletion(-) diff -puN arch/x86/include/asm/pkeys.h~pkeys-112-mask-off-correct-vm_flags arch/x86/include/asm/pkeys.h --- a/arch/x86/include/asm/pkeys.h~pkeys-112-mask-off-correct-vm_flags 2016-04-11 08:38:41.373273394 -0700 +++ b/arch/x86/include/asm/pkeys.h 2016-04-11 08:38:41.380273711 -0700 @@ -38,4 +38,6 @@ static inline int arch_override_mprotect extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long init_val); +#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | VM_PKEY_BIT3) + #endif /*_ASM_X86_PKEYS_H */ diff -puN include/linux/pkeys.h~pkeys-112-mask-off-correct-vm_flags include/linux/pkeys.h --- a/include/linux/pkeys.h~pkeys-112-mask-off-correct-vm_flags 2016-04-11 08:38:41.375273485 -0700 +++ b/include/linux/pkeys.h 2016-04-11 08:38:41.381273757 -0700 @@ -16,6 +16,7 @@ #define execute_only_pkey(mm) (0) #define arch_override_mprotect_pkey(vma, prot, pkey) (0) #define PKEY_DEDICATED_EXECUTE_ONLY 0 +#define ARCH_VM_PKEY_FLAGS 0 #endif /* ! CONFIG_ARCH_HAS_PKEYS */ /* diff -puN mm/mprotect.c~pkeys-112-mask-off-correct-vm_flags mm/mprotect.c --- a/mm/mprotect.c~pkeys-112-mask-off-correct-vm_flags 2016-04-11 08:38:41.377273575 -0700 +++ b/mm/mprotect.c 2016-04-11 08:38:41.381273757 -0700 @@ -410,6 +410,7 @@ static int do_mprotect_pkey(unsigned lon prev = vma; for (nstart = start ; ; ) { + unsigned long mask_off_old_flags; unsigned long newflags; int vma_pkey; @@ -419,9 +420,17 @@ static int do_mprotect_pkey(unsigned lon if (rier && (vma->vm_flags & VM_MAYEXEC)) prot |= PROT_EXEC; + /* + * Each mprotect() call explicitly passes r/w/x permissions. + * If a permission is not passed to mprotect(), it must be + * cleared from the VMA. + */ + mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC | + ARCH_VM_PKEY_FLAGS; + vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); newflags = calc_vm_prot_bits(prot, vma_pkey); - newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); + newflags |= (vma->vm_flags & ~mask_off_old_flags); /* newflags >> 4 shift VM_MAY% in place of VM_% */ if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { _