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 my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>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()
/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>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/mem.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 7e4a9d1296bb..6e0cbe092220 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -340,6 +340,11 @@ static const struct vm_operations_struct mmap_mem_ops = {
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;
--
2.13.0