[PATCH 13/25] mm: factor out VMA fault permission checking

From: Dave Hansen
Date: Mon Sep 28 2015 - 15:22:31 EST



From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
---

b/mm/gup.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff -puN mm/gup.c~pkeys-10-pte-fault mm/gup.c
--- a/mm/gup.c~pkeys-10-pte-fault 2015-09-28 11:39:46.790221164 -0700
+++ b/mm/gup.c 2015-09-28 11:39:46.794221345 -0700
@@ -554,6 +554,17 @@ 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 =
+ (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
@@ -585,15 +596,13 @@ int fixup_user_fault(struct task_struct
unsigned long address, unsigned int fault_flags)
{
struct vm_area_struct *vma;
- vm_flags_t vm_flags;
int ret;

vma = find_extend_vma(mm, address);
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);
_
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/