[src/trunk]: src/usr.bin/xlint lint: fix memory allocation (since 2021-08-28)

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

details:   https://anonhg.NetBSD.org/src/rev/4506443a72e8
branches:  trunk
changeset: 1023275:4506443a72e8
user:      rillig <rillig%NetBSD.org@localhost>
date:      Tue Aug 31 17:22:24 2021 +0000

description:
lint: fix memory allocation (since 2021-08-28)

In mem1.c 1.50 and mem2.c 1.13 from 2021-08-28, I accidentally changed
the initialization of mblklen from round_up to round_down, trying to
avoid a division instruction.

On NetBSD x86_64 this resulted in a few more malloc calls, but on Cygwin
with its 64k pagesize, mblklen became 0.  Later, the function xalloc in
lint2 called xalloc(mblklen) and blindly assumed that the returned
memory would be large enough.  This in turn led to out-of-bounds memory
access and crashes.  Lint1 was not affected since it adjust mblklen
during runtime if it gets too small.

diffstat:

 usr.bin/xlint/common/externs.h |   3 ++-
 usr.bin/xlint/common/mem.c     |  16 ++++++++++++++--
 usr.bin/xlint/lint1/mem1.c     |   8 +++-----
 usr.bin/xlint/lint2/mem2.c     |   8 +++-----
 4 files changed, 22 insertions(+), 13 deletions(-)

diffs (122 lines):

diff -r cbe4356d3dd8 -r 4506443a72e8 usr.bin/xlint/common/externs.h
--- a/usr.bin/xlint/common/externs.h    Tue Aug 31 11:16:00 2021 +0000
+++ b/usr.bin/xlint/common/externs.h    Tue Aug 31 17:22:24 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: externs.h,v 1.20 2021/08/22 15:06:49 rillig Exp $      */
+/*     $NetBSD: externs.h,v 1.21 2021/08/31 17:22:24 rillig Exp $      */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -45,6 +45,7 @@
 /*
  * mem.c
  */
+extern size_t  mem_block_size(void);
 extern void    *xmalloc(size_t);
 extern void    *xcalloc(size_t, size_t);
 extern void    *xrealloc(void *, size_t);
diff -r cbe4356d3dd8 -r 4506443a72e8 usr.bin/xlint/common/mem.c
--- a/usr.bin/xlint/common/mem.c        Tue Aug 31 11:16:00 2021 +0000
+++ b/usr.bin/xlint/common/mem.c        Tue Aug 31 17:22:24 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mem.c,v 1.18 2021/08/28 13:29:26 rillig Exp $  */
+/*     $NetBSD: mem.c,v 1.19 2021/08/31 17:22:24 rillig Exp $  */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,15 +37,27 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: mem.c,v 1.18 2021/08/28 13:29:26 rillig Exp $");
+__RCSID("$NetBSD: mem.c,v 1.19 2021/08/31 17:22:24 rillig Exp $");
 #endif
 
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #include "lint.h"
 
+#if defined(IS_LINT1) || defined(IS_LINT2)
+size_t
+mem_block_size(void)
+{
+       unsigned int pagesize;
+
+       pagesize = (unsigned int)getpagesize();
+       return (MBLKSIZ + pagesize - 1) / pagesize * pagesize;
+}
+#endif
+
 static void *
 not_null(void *ptr)
 {
diff -r cbe4356d3dd8 -r 4506443a72e8 usr.bin/xlint/lint1/mem1.c
--- a/usr.bin/xlint/lint1/mem1.c        Tue Aug 31 11:16:00 2021 +0000
+++ b/usr.bin/xlint/lint1/mem1.c        Tue Aug 31 17:22:24 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mem1.c,v 1.51 2021/08/28 13:29:26 rillig Exp $ */
+/*     $NetBSD: mem1.c,v 1.52 2021/08/31 17:22:25 rillig Exp $ */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,14 +37,12 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: mem1.c,v 1.51 2021/08/28 13:29:26 rillig Exp $");
+__RCSID("$NetBSD: mem1.c,v 1.52 2021/08/31 17:22:25 rillig Exp $");
 #endif
 
-#include <sys/types.h>
 #include <sys/param.h>
 #include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
 
 #include "lint1.h"
 
@@ -286,7 +284,7 @@
 initmem(void)
 {
 
-       mblklen = MBLKSIZ - MBLKSIZ % (unsigned int)getpagesize();
+       mblklen = mem_block_size();
        mblks = xcalloc(nmblks = ML_INC, sizeof(*mblks));
 }
 
diff -r cbe4356d3dd8 -r 4506443a72e8 usr.bin/xlint/lint2/mem2.c
--- a/usr.bin/xlint/lint2/mem2.c        Tue Aug 31 11:16:00 2021 +0000
+++ b/usr.bin/xlint/lint2/mem2.c        Tue Aug 31 17:22:24 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mem2.c,v 1.13 2021/08/28 12:59:25 rillig Exp $ */
+/*     $NetBSD: mem2.c,v 1.14 2021/08/31 17:22:25 rillig Exp $ */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,13 +37,11 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: mem2.c,v 1.13 2021/08/28 12:59:25 rillig Exp $");
+__RCSID("$NetBSD: mem2.c,v 1.14 2021/08/31 17:22:25 rillig Exp $");
 #endif
 
 #include <sys/param.h>
-#include <sys/types.h>
 #include <string.h>
-#include <unistd.h>
 
 #include "lint2.h"
 
@@ -60,7 +58,7 @@
 initmem(void)
 {
 
-       mblklen = MBLKSIZ - MBLKSIZ % (unsigned int)getpagesize();
+       mblklen = mem_block_size();
        nxtfree = mblklen;
 }