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authorJulius Werner <jwerner@chromium.org>2017-05-12 14:42:58 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-05-25 14:30:18 +0200
commit837bfdb41337fc6b82dbde4b2ec3ce923845049f (patch)
parent52cf24769487de7100d824e8c12ecc310de841d7 (diff)
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>
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index e901463d4972..0975d23031ea 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -343,6 +343,11 @@ 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;