Add buffer corruption protection (RedZone) for kernel's malloc(9).

It detects both: buffer underflows and buffer overflows bugs at runtime
(on free(9) and realloc(9)) and prints backtraces from where memory was
allocated and from where it was freed.

Tested by:	kris

2 files changed, 219 insertions, 0 deletions

diff --git a/sys/vm/redzone.c b/sys/vm/redzone.c
new file mode 100644
index 0000000..5598b5d
--- /dev/null
+++ b/sys/vm/redzone.c
@@ -0,0 +1,181 @@
+/*-
+ * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/stack.h>
+#include <sys/sysctl.h>
+
+#include <vm/redzone.h>
+
+
+SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW, NULL, "RedZone data");
+static u_long redzone_extra_mem = 0;
+SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem,
+    0, "Extra memory allocated by redzone");     
+static int redzone_panic = 0;
+TUNABLE_INT("vm.redzone.panic", &redzone_panic);
+SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RW, &redzone_panic, 0,
+    "Panic when buffer corruption is detected");     
+
+#define	REDZONE_CHSIZE	(16)
+#define	REDZONE_CFSIZE	(16)
+#define	REDZONE_HSIZE	(sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
+#define	REDZONE_FSIZE	(REDZONE_CFSIZE)
+
+static u_long
+redzone_roundup(u_long n)
+{
+
+	if (n <= 128)
+		return (128);
+	else if (n <= 256)
+		return (256);
+	else if (n <= 512)
+		return (512);
+	else if (n <= 1024)
+		return (1024);
+	else if (n <= 2048)
+		return (2048);
+	return (PAGE_SIZE);
+}
+
+u_long
+redzone_get_size(caddr_t naddr)
+{
+	u_long nsize;
+
+	bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
+	return (nsize);
+}
+
+u_long
+redzone_size_ntor(u_long nsize)
+{
+
+	return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
+}
+
+void *
+redzone_addr_ntor(caddr_t naddr)
+{
+
+	return (naddr - redzone_roundup(redzone_get_size(naddr)));
+}
+
+/*
+ * Set redzones and remember allocation backtrace.
+ */
+void *
+redzone_setup(caddr_t raddr, u_long nsize)
+{
+	struct stack st;
+	caddr_t haddr, faddr;
+
+	atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
+
+	haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
+	faddr = haddr + REDZONE_HSIZE + nsize;
+
+	/* Redzone header. */
+	stack_save(&st);
+	bcopy(&st, haddr, sizeof(st));
+	haddr += sizeof(st);
+	bcopy(&nsize, haddr, sizeof(nsize));
+	haddr += sizeof(nsize);
+	memset(haddr, 0x42, REDZONE_CHSIZE);
+	haddr += REDZONE_CHSIZE;
+
+	/* Redzone footer. */
+	memset(faddr, 0x42, REDZONE_CFSIZE);
+
+	return (haddr);
+}
+
+/*
+ * Verify redzones.
+ * This function is called on free() and realloc().
+ */
+void
+redzone_check(caddr_t naddr)
+{
+	struct stack ast, fst;
+	caddr_t haddr, faddr;
+	u_int ncorruptions;
+	u_long nsize;
+	int i;
+
+	haddr = naddr - REDZONE_HSIZE;
+	bcopy(haddr, &ast, sizeof(ast));
+	haddr += sizeof(ast);
+	bcopy(haddr, &nsize, sizeof(nsize));
+	haddr += sizeof(nsize);
+
+	atomic_subtract_long(&redzone_extra_mem,
+	    redzone_size_ntor(nsize) - nsize);
+
+	/* Look for buffer underflow. */
+	ncorruptions = 0;
+	for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
+		if (*(u_char *)haddr != 0x42)
+			ncorruptions++;
+	}
+	if (ncorruptions > 0) {
+		printf("REDZONE: Buffer underflow detected. %u byte%s "
+		    "corrupted before %p (%lu bytes allocated).\n",
+		    ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
+		printf("Allocation backtrace:\n");
+		stack_print(&ast);
+		printf("Free backtrace:\n");
+		stack_save(&fst);
+		stack_print(&fst);
+		if (redzone_panic)
+			panic("Stopping here.");
+	}
+	faddr = naddr + nsize;
+	/* Look for buffer overflow. */
+	ncorruptions = 0;
+	for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
+		if (*(u_char *)faddr != 0x42)
+			ncorruptions++;
+	}
+	if (ncorruptions > 0) {
+		printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
+		    "after %p (%lu bytes allocated).\n", ncorruptions,
+		    ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
+		printf("Allocation backtrace:\n");
+		stack_print(&ast);
+		printf("Free backtrace:\n");
+		stack_save(&fst);
+		stack_print(&fst);
+		if (redzone_panic)
+			panic("Stopping here.");
+	}
+}
diff --git a/sys/vm/redzone.h b/sys/vm/redzone.h
new file mode 100644
index 0000000..8738d7e
--- /dev/null
+++ b/sys/vm/redzone.h
@@ -0,0 +1,38 @@
+/*-
+ * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef	_VM_REDZONE_H_
+#define	_VM_REDZONE_H_
+
+u_long redzone_get_size(caddr_t naddr);
+u_long redzone_size_ntor(u_long nsize);
+void *redzone_addr_ntor(caddr_t naddr);
+void *redzone_setup(caddr_t raddr, u_long nsize);
+void redzone_check(caddr_t naddr);
+
+#endif	/* _VM_REDZONE_H_ */