From b299cde245b0b76c977f4291162cf668e087b408 Mon Sep 17 00:00:00 2001 From: Julius Werner Date: Fri, 12 May 2017 14:42:58 -0700 Subject: [PATCH] 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 Cc: stable Signed-off-by: Greg Kroah-Hartman --- 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; -- 2.20.1