[src/trunk]: src/sys/kern rasctl(2): Avoid overflow in address range arithmetic.

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/de91bd4987a8
branches:  trunk
changeset: 368765:de91bd4987a8
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Wed Aug 03 09:40:25 2022 +0000

description:
rasctl(2): Avoid overflow in address range arithmetic.

Remove various contortions to suppress warnings.  Rely on
-Wno-type-limits instead.

Reported-by: syzbot+8b0f1ced3fce82031535%syzkaller.appspotmail.com@localhost
https://syzkaller.appspot.com/bug?id=e9055200701cffd653d5b13491d85c34e07f06a3

diffstat:

 sys/kern/kern_ras.c |  25 ++++++-------------------
 1 files changed, 6 insertions(+), 19 deletions(-)

diffs (55 lines):

diff -r 9e65c18677ec -r de91bd4987a8 sys/kern/kern_ras.c
--- a/sys/kern/kern_ras.c       Wed Aug 03 09:37:36 2022 +0000
+++ b/sys/kern/kern_ras.c       Wed Aug 03 09:40:25 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_ras.c,v 1.40 2019/12/14 16:58:25 riastradh Exp $  */
+/*     $NetBSD: kern_ras.c,v 1.41 2022/08/03 09:40:25 riastradh Exp $  */
 
 /*-
  * Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_ras.c,v 1.40 2019/12/14 16:58:25 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_ras.c,v 1.41 2022/08/03 09:40:25 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -156,14 +156,6 @@
 
 #if defined(__HAVE_RAS)
 
-#if __GNUC_PREREQ__(4, 8)
-#define        __WARNING_PUSH_LESS_NULL_PTR    _Pragma("GCC diagnostic push")  _Pragma("GCC diagnostic ignored \"-Wextra\"")
-#define        __WARNING_POP_LESS_NULL_PTR     _Pragma("GCC diagnostic pop")
-#else
-#define        __WARNING_PUSH_LESS_NULL_PTR
-#define        __WARNING_POP_LESS_NULL_PTR
-#endif
-
 /*
  * Install the new sequence.  If it already exists, return
  * an error.
@@ -180,17 +172,12 @@
        if (len == 0)
                return EINVAL;
 
-       endaddr = (char *)addr + len;
-
-       /* Do not warn about < NULL pointer comparison */
-       __WARNING_PUSH_LESS_NULL_PTR
-       if (addr < (void *)VM_MIN_ADDRESS || addr > (void *)VM_MAXUSER_ADDRESS)
+       if ((uintptr_t)addr < VM_MIN_ADDRESS ||
+           (uintptr_t)addr > VM_MAXUSER_ADDRESS)
                return EINVAL;
-       if (endaddr > (void *)VM_MAXUSER_ADDRESS)
+       if (len > VM_MAXUSER_ADDRESS - (uintptr_t)addr)
                return EINVAL;
-       if (endaddr < addr)
-               return EINVAL;
-       __WARNING_POP_LESS_NULL_PTR
+       endaddr = (char *)addr + len;
 
        newrp = kmem_alloc(sizeof(*newrp), KM_SLEEP);
        newrp->ras_startaddr = addr;