linux-kernel - [tip:mm/pkeys] mm/gup: Factor out VMA fault permission checking

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Date:	Thu, 18 Feb 2016 12:21:30 -0800
From:	tip-bot for Dave Hansen <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	aneesh.kumar@...ux.vnet.ibm.com, dvlasenk@...hat.com,
	jason.low2@...com, bp@...en8.de, torvalds@...ux-foundation.org,
	dan.j.williams@...el.com, riel@...hat.com, dave@...1.net,
	kirill.shutemov@...ux.intel.com, akpm@...ux-foundation.org,
	hpa@...or.com, linux-kernel@...r.kernel.org, brgerst@...il.com,
	luto@...capital.net, dave.hansen@...ux.intel.com,
	sasha.levin@...cle.com, dingel@...ux.vnet.ibm.com,
	peterz@...radead.org, tglx@...utronix.de, mingo@...nel.org,
	emunson@...mai.com
Subject: [tip:mm/pkeys] mm/gup: Factor out VMA fault permission checking

Commit-ID:  d4925e00d59698a201231cf99dce47d8b922bb34
Gitweb:     http://git.kernel.org/tip/d4925e00d59698a201231cf99dce47d8b922bb34
Author:     Dave Hansen <dave.hansen@...ux.intel.com>
AuthorDate: Fri, 12 Feb 2016 13:02:16 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 18 Feb 2016 09:32:43 +0100

mm/gup: Factor out VMA fault permission checking

This code matches a fault condition up with the VMA and ensures
that the VMA allows the fault to be handled instead of just
erroring out.

We will be extending this in a moment to comprehend protection
keys.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Dave Hansen <dave@...1.net>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Dominik Dingel <dingel@...ux.vnet.ibm.com>
Cc: Eric B Munson <emunson@...mai.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Jason Low <jason.low2@...com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Sasha Levin <sasha.levin@...cle.com>
Cc: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org
Link: http://lkml.kernel.org/r/20160212210216.C3824032@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 mm/gup.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index de24ef4..b935c2c 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -610,6 +610,18 @@ next_page:
 }
 EXPORT_SYMBOL(__get_user_pages);
 
+bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags)
+{
+	vm_flags_t vm_flags;
+
+	vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
+
+	if (!(vm_flags & vma->vm_flags))
+		return false;
+
+	return true;
+}
+
 /*
  * fixup_user_fault() - manually resolve a user page fault
  * @tsk:	the task_struct to use for page fault accounting, or
@@ -645,7 +657,6 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
 		     bool *unlocked)
 {
 	struct vm_area_struct *vma;
-	vm_flags_t vm_flags;
 	int ret, major = 0;
 
 	if (unlocked)
@@ -656,8 +667,7 @@ retry:
 	if (!vma || address < vma->vm_start)
 		return -EFAULT;
 
-	vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
-	if (!(vm_flags & vma->vm_flags))
+	if (!vma_permits_fault(vma, fault_flags))
 		return -EFAULT;
 
 	ret = handle_mm_fault(mm, vma, address, fault_flags);