[PATCH] /dev/mem: validate mmap requests
Add a hook so architectures can validate /dev/mem mmap requests.
This is analogous to validation we already perform in the read/write
paths.
The identity mapping scheme used on ia64 requires that each 16MB or
64MB granule be accessed with exactly one attribute (write-back or
uncacheable). This avoids "attribute aliasing", which can cause a
machine check.
Sample problem scenario:
- Machine supports VGA, so it has uncacheable (UC) MMIO at 640K-768K
- efi_memmap_init() discards any write-back (WB) memory in the first granule
- Application (e.g., "hwinfo") mmaps /dev/mem, offset 0
- hwinfo receives UC mapping (the default, since memmap says "no WB here")
- Machine check abort (on chipsets that don't support UC access to WB
memory, e.g., sx1000)
In the scenario above, the only choices are
- Use WB for hwinfo mmap. Can't do this because it causes attribute
aliasing with the UC mapping for the VGA MMIO space.
- Use UC for hwinfo mmap. Can't do this because the chipset may not
support UC for that region.
- Disallow the hwinfo mmap with -EINVAL. That's what this patch does.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index ce3ff86..5b2d180 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -101,6 +101,11 @@
return 1;
}
+
+static inline int valid_mmap_phys_addr_range(unsigned long addr, size_t *size)
+{
+ return 1;
+}
#endif
/*
@@ -244,15 +249,20 @@
static int mmap_mem(struct file * file, struct vm_area_struct * vma)
{
+ size_t size = vma->vm_end - vma->vm_start;
+
+ if (!valid_mmap_phys_addr_range(vma->vm_pgoff << PAGE_SHIFT, &size))
+ return -EINVAL;
+
vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
- vma->vm_end - vma->vm_start,
+ size,
vma->vm_page_prot);
/* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
if (remap_pfn_range(vma,
vma->vm_start,
vma->vm_pgoff,
- vma->vm_end-vma->vm_start,
+ size,
vma->vm_page_prot))
return -EAGAIN;
return 0;