svn commit: r348843 - head/sys/vm

[Doug Moore]

Author: dougm
Date: Mon Jun 10 03:07:10 2019
New Revision: 348843
URL: https://svnweb.freebsd.org/changeset/base/348843

Log:
  There are times when a len==0 parameter to mmap is okay. But on a
  32-bit machine, a len parameter just a few bytes short of 4G, rounded
  up to a page boundary and hitting zero then, is not okay. Return
  failure in that case.
  
  Reported by: pho
  Reviewed by: alc, kib (mentor)
  Tested by: pho
  Differential Revision: https://reviews.freebsd.org/D20580

Modified:
  head/sys/vm/vm_mmap.c

Modified: head/sys/vm/vm_mmap.c
==============================================================================
--- head/sys/vm/vm_mmap.c	Sun Jun  9 22:55:21 2019	(r348842)
+++ head/sys/vm/vm_mmap.c	Mon Jun 10 03:07:10 2019	(r348843)
@@ -257,7 +257,10 @@ kern_mmap(struct thread *td, uintptr_t addr0, size_t s
 
 	/* Adjust size for rounding (on both ends). */
 	size += pageoff;			/* low end... */
-	size = (vm_size_t) round_page(size);	/* hi end */
+	/* Check for rounding up to zero. */
+	if (round_page(size) < size)
+		return (EINVAL);
+	size = round_page(size);		/* hi end */
 
 	/* Ensure alignment is at least a page and fits in a pointer. */
 	align = flags & MAP_ALIGNMENT_MASK;