Commit ea3c00fd authored May 12, 2017 by Julius Werner Committed by Greg Kroah-Hartman May 25, 2017

drivers: char: mem: Check for address space wraparound with mmap()



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@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent cc932a80

drivers/char/mem.c

+5 −0

Original line number	Original line	Diff line number	Diff line
	@@ -329,6 +329,11 @@ static const struct vm_operations_struct mmap_mem_ops = {
	static int mmap_mem(struct file file, struct vm_area_struct vma)		static int mmap_mem(struct file file, struct vm_area_struct vma)
	{		{
	size_t size = vma->vm_end - vma->vm_start;		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))		if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))
	return -EINVAL;		return -EINVAL;