This is a note to let you know that I've just added the patch titled
drivers: char: mem: Check for address space wraparound with mmap()
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drivers-char-mem-check-for-address-space-wraparound-with-mmap.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b299cde245b0b76c977f4291162cf668e087b408 Mon Sep 17 00:00:00 2001
From: Julius Werner <jwerner@xxxxxxxxxxxx>
Date: Fri, 12 May 2017 14:42:58 -0700
Subject: drivers: char: mem: Check for address space wraparound with mmap()
From: Julius Werner <jwerner@xxxxxxxxxxxx>
commit b299cde245b0b76c977f4291162cf668e087b408 upstream.
/dev/mem currently allows mmap() mappings that wrap around the end of
the physical address space, which should probably be illegal. It
circumvents the existing STRICT_DEVMEM permission check because the loop
immediately terminates (as the start address is already higher than the
end address). On the x86_64 architecture it will then cause a panic
(from the BUG(start >= end) in arch/x86/mm/pat.c:reserve_memtype()).
This patch adds an explicit check to make sure offset + size will not
wrap around in the physical address type.
Signed-off-by: Julius Werner <jwerner@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/mem.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -340,6 +340,11 @@ static const struct vm_operations_struct
static int mmap_mem(struct file *file, struct vm_area_struct *vma)
{
size_t size = vma->vm_end - vma->vm_start;
+ phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
+
+ /* It's illegal to wrap around the end of the physical address space. */
+ if (offset + (phys_addr_t)size < offset)
+ return -EINVAL;
if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
return -EINVAL;
Patches currently in stable-queue which might be from jwerner@xxxxxxxxxxxx are
queue-4.9/drivers-char-mem-check-for-address-space-wraparound-with-mmap.patch