Commit d4925e00 authored Feb 12, 2016 by Dave Hansen Committed by Ingo Molnar Feb 18, 2016

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@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dominik Dingel <dingel@linux.vnet.ibm.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210216.C3824032@viggo.jf.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent a927cb83

mm/gup.c

+13 −3

Original line number	Diff line number	Diff line
		@@ -610,6 +610,18 @@ long __get_user_pages(struct task_struct tsk, struct mm_struct mm,
		}
		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 @@ int fixup_user_fault(struct task_struct tsk, struct mm_struct mm,
		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);