Patch "drivers: char: mem: Check for address space wraparound with mmap()" has been added to the 4.4-stable tree

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 4.4-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-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Julius Werner <[email protected]>
Date: Fri, 12 May 2017 14:42:58 -0700
Subject: drivers: char: mem: Check for address space wraparound with mmap()

From: Julius Werner <[email protected]>

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.

---
 drivers/char/mem.c |    5 +++++
 1 file changed, 5 insertions(+)

@@ -343,6 +343,11 @@ 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 [email protected] are

queue-4.4/drivers-char-mem-check-for-address-space-wraparound-with-mmap.patch