From: Julius Werner Date: Fri, 2 Jun 2017 22:36:39 +0000 (-0700) Subject: drivers: char: mem: Fix wraparound check to allow mappings up to the end X-Git-Tag: v3.2.93~51 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e0d4246a9441204e5ff5b6de69d72443b80de485;p=thirdparty%2Fkernel%2Fstable.git drivers: char: mem: Fix wraparound check to allow mappings up to the end commit 32829da54d9368103a2f03269a5120aa9ee4d5da upstream. A recent fix to /dev/mem prevents mappings from wrapping around the end of physical address space. However, the check was written in a way that also prevents a mapping reaching just up to the end of physical address space, which may be a valid use case (especially on 32-bit systems). This patch fixes it by checking the last mapped address (instead of the first address behind that) for overflow. Fixes: b299cde245 ("drivers: char: mem: Check for address space wraparound with mmap()") Reported-by: Nico Huber Signed-off-by: Julius Werner Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 1c8cfa67f7e1f..d78365603952d 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -325,7 +325,7 @@ static int mmap_mem(struct file *file, struct vm_area_struct *vma) 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) + if (offset + (phys_addr_t)size - 1 < offset) return -EINVAL; if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))