[src/trunk]: src/sys/kern in bounds_check_with_*, reject negative block numbe...

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

details:   https://anonhg.NetBSD.org/src/rev/4aca1d6c057c
branches:  trunk
changeset: 338208:4aca1d6c057c
user:      chs <chs%NetBSD.org@localhost>
date:      Thu May 14 17:31:24 2015 +0000

description:
in bounds_check_with_*, reject negative block numbers and avoid
a potential overflow in calculating the size of the request.

diffstat:

 sys/kern/subr_disk.c |  33 ++++++++++++++++++++++++++++-----
 1 files changed, 28 insertions(+), 5 deletions(-)

diffs (68 lines):

diff -r 8a614dc29bdd -r 4aca1d6c057c sys/kern/subr_disk.c
--- a/sys/kern/subr_disk.c      Thu May 14 17:15:56 2015 +0000
+++ b/sys/kern/subr_disk.c      Thu May 14 17:31:24 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_disk.c,v 1.112 2015/05/05 22:09:24 mlelstv Exp $  */
+/*     $NetBSD: subr_disk.c,v 1.113 2015/05/14 17:31:24 chs Exp $      */
 
 /*-
  * Copyright (c) 1996, 1997, 1999, 2000, 2009 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_disk.c,v 1.112 2015/05/05 22:09:24 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_disk.c,v 1.113 2015/05/14 17:31:24 chs Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -314,7 +314,18 @@
 {
        int64_t sz;
 
-       sz = howmany(bp->b_bcount, secsize);
+       if (bp->b_blkno < 0) {
+               /* Reject negative offsets immediately. */
+               bp->b_error = EINVAL;
+               return 0;
+       }
+
+       sz = howmany((int64_t)bp->b_bcount, secsize);
+
+       /*
+        * bp->b_bcount is a 32-bit value, and we rejected a negative
+        * bp->b_blkno already, so "bp->b_blkno + sz" cannot overflow.
+        */
 
        if (bp->b_blkno + sz > mediasize) {
                sz = mediasize - bp->b_blkno;
@@ -348,6 +359,12 @@
        uint64_t p_size, p_offset, labelsector;
        int64_t sz;
 
+       if (bp->b_blkno < 0) {
+               /* Reject negative offsets immediately. */
+               bp->b_error = EINVAL;
+               return -1;
+       }
+
        /* Protect against division by zero. XXX: Should never happen?!?! */
        if (lp->d_secpercyl == 0) {
                bp->b_error = EINVAL;
@@ -363,8 +380,14 @@
 #endif
        labelsector = (labelsector + dk->dk_labelsector) << dk->dk_blkshift;
 
-       sz = howmany(bp->b_bcount, DEV_BSIZE);
-       if ((bp->b_blkno + sz) > p_size) {
+       sz = howmany((int64_t)bp->b_bcount, DEV_BSIZE);
+
+       /*
+        * bp->b_bcount is a 32-bit value, and we rejected a negative
+        * bp->b_blkno already, so "bp->b_blkno + sz" cannot overflow.
+        */
+
+       if (bp->b_blkno + sz > p_size) {
                sz = p_size - bp->b_blkno;
                if (sz == 0) {
                        /* If exactly at end of disk, return EOF. */