diff --git a/src/lib/libc/stdlib/malloc.c b/src/lib/libc/stdlib/malloc.c
index dd4c4872..36d2d717 100644
--- a/src/lib/libc/stdlib/malloc.c
+++ b/src/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: malloc.c,v 1.176 2015/09/13 20:29:23 guenther Exp $	*/
+/*	$OpenBSD: malloc.c,v 1.177 2015/12/09 02:45:23 tedu Exp $	*/
 /*
  * Copyright (c) 2008, 2010, 2011 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -185,12 +185,14 @@ struct malloc_readonly {
 	int	malloc_move;		/* move allocations to end of page? */
 	int	malloc_realloc;		/* always realloc? */
 	int	malloc_xmalloc;		/* xmalloc behaviour? */
+	size_t	malloc_canaries;	/* use canaries after chunks? */
 	size_t	malloc_guard;		/* use guard pages after allocations? */
 	u_int	malloc_cache;		/* free pages we cache */
 #ifdef MALLOC_STATS
 	int	malloc_stats;		/* dump statistics at end */
 #endif
 	u_int32_t malloc_canary;	/* Matched against ones in malloc_pool */
+	uintptr_t malloc_chunk_canary;
 };
 
 /* This object is mapped PROT_READ after initialisation to prevent tampering */
@@ -526,6 +528,12 @@ omalloc_init(struct dir_info **dp)
 			case 'A':
 				mopts.malloc_abort = 1;
 				break;
+			case 'c':
+				mopts.malloc_canaries = 0;
+				break;
+			case 'C':
+				mopts.malloc_canaries = sizeof(void *);
+				break;
 #ifdef MALLOC_STATS
 			case 'd':
 				mopts.malloc_stats = 0;
@@ -619,6 +627,9 @@ omalloc_init(struct dir_info **dp)
 	while ((mopts.malloc_canary = arc4random()) == 0)
 		;
 
+	arc4random_buf(&mopts.malloc_chunk_canary,
+	    sizeof(mopts.malloc_chunk_canary));
+
 	/*
 	 * Allocate dir_info with a guard page on either side. Also
 	 * randomise offset inside the page at which the dir_info
@@ -984,8 +995,15 @@ malloc_bytes(struct dir_info *d, size_t size, void *f)
 	k += (lp - bp->bits) * MALLOC_BITS;
 	k <<= bp->shift;
 
+	if (mopts.malloc_canaries && bp->size > 0) {
+		char *end = (char *)bp->page + k + bp->size;
+		uintptr_t *canary = (uintptr_t *)(end - mopts.malloc_canaries);
+		*canary = mopts.malloc_chunk_canary ^ hash(canary);
+	}
+
 	if (mopts.malloc_junk == 2 && bp->size > 0)
-		memset((char *)bp->page + k, SOME_JUNK, bp->size);
+		memset((char *)bp->page + k, SOME_JUNK,
+		    bp->size - mopts.malloc_canaries);
 	return ((char *)bp->page + k);
 }
 
@@ -999,6 +1017,13 @@ find_chunknum(struct dir_info *d, struct region_info *r, void *ptr)
 	if (info->canary != d->canary1)
 		wrterror("chunk info corrupted", NULL);
 
+	if (mopts.malloc_canaries && info->size > 0) {
+		char *end = (char *)ptr + info->size;
+		uintptr_t *canary = (uintptr_t *)(end - mopts.malloc_canaries);
+		if (*canary != (mopts.malloc_chunk_canary ^ hash(canary)))
+			wrterror("chunk canary corrupted", ptr);
+	}
+
 	/* Find the chunk number on the page */
 	chunknum = ((uintptr_t)ptr & MALLOC_PAGEMASK) >> info->shift;
 
@@ -1121,7 +1146,7 @@ omalloc(size_t sz, int zero_fill, void *f)
 		/* takes care of SOME_JUNK */
 		p = malloc_bytes(pool, sz, f);
 		if (zero_fill && p != NULL && sz > 0)
-			memset(p, 0, sz);
+			memset(p, 0, sz - mopts.malloc_canaries);
 	}
 
 	return p;
@@ -1176,6 +1201,8 @@ malloc(size_t size)
 		malloc_recurse();
 		return NULL;
 	}
+	if (size > 0 && size <= MALLOC_MAXCHUNK)
+		size += mopts.malloc_canaries;
 	r = omalloc(size, 0, CALLER);
 	malloc_active--;
 	_MALLOC_UNLOCK();
@@ -1189,6 +1216,30 @@ malloc(size_t size)
 }
 /*DEF_STRONG(malloc);*/
 
+static void
+validate_junk(void *p) {
+	struct region_info *r;
+	struct dir_info *pool = getpool();
+	size_t byte, sz;
+
+	if (p == NULL)
+		return;
+	r = find(pool, p);
+	if (r == NULL)
+		wrterror("bogus pointer in validate_junk", p);
+	REALSIZE(sz, r);
+	if (sz > 0 && sz <= MALLOC_MAXCHUNK)
+		sz -= mopts.malloc_canaries;
+	if (sz > 32)
+		sz = 32;
+	for (byte = 0; byte < sz; byte++) {
+		if (((unsigned char *)p)[byte] != SOME_FREEJUNK) {
+			wrterror("use after free", p);
+			return;
+		}
+	}
+}
+
 static void
 ofree(void *p)
 {
@@ -1242,7 +1293,7 @@ ofree(void *p)
 		int i;
 
 		if (mopts.malloc_junk && sz > 0)
-			memset(p, SOME_FREEJUNK, sz);
+			memset(p, SOME_FREEJUNK, sz - mopts.malloc_canaries);
 		if (!mopts.malloc_freenow) {
 			if (find_chunknum(pool, r, p) == -1)
 				return;
@@ -1253,6 +1304,8 @@ ofree(void *p)
 				wrterror("double free", p);
 				return;
 			}
+			if (mopts.malloc_junk)
+				validate_junk(p);
 			pool->delayed_chunks[i] = tmp;
 		}
 		if (p != NULL) {
@@ -1386,16 +1439,25 @@ gotit:
 		}
 	}
 	if (newsz <= oldsz && newsz > oldsz / 2 && !mopts.malloc_realloc) {
-		if (mopts.malloc_junk == 2 && newsz > 0)
-			memset((char *)p + newsz, SOME_JUNK, oldsz - newsz);
+		if (mopts.malloc_junk == 2 && newsz > 0) {
+			size_t usable_oldsz = oldsz;
+			if (oldsz <= MALLOC_MAXCHUNK)
+				usable_oldsz -= mopts.malloc_canaries;
+			if (newsz < usable_oldsz)
+				memset((char *)p + newsz, SOME_JUNK, usable_oldsz - newsz);
+		}
 		STATS_SETF(r, f);
 		return p;
 	} else if (newsz != oldsz || mopts.malloc_realloc) {
 		q = omalloc(newsz, 0, f);
 		if (q == NULL)
 			return NULL;
-		if (newsz != 0 && oldsz != 0)
-			memcpy(q, p, oldsz < newsz ? oldsz : newsz);
+		if (newsz != 0 && oldsz != 0) {
+			size_t copysz = oldsz < newsz ? oldsz : newsz;
+			if (copysz <= MALLOC_MAXCHUNK)
+				copysz -= mopts.malloc_canaries;
+			memcpy(q, p, copysz);
+		}
 		ofree(p);
 		return q;
 	} else {
@@ -1420,6 +1482,8 @@ realloc(void *ptr, size_t size)
 		malloc_recurse();
 		return NULL;
 	}
+	if (size > 0 && size <= MALLOC_MAXCHUNK)
+		size += mopts.malloc_canaries;
 	r = orealloc(ptr, size, CALLER);
 
 	malloc_active--;
@@ -1468,6 +1532,8 @@ calloc(size_t nmemb, size_t size)
 	}
 
 	size *= nmemb;
+	if (size > 0 && size <= MALLOC_MAXCHUNK)
+		size += mopts.malloc_canaries;
 	r = omalloc(size, 1, CALLER);
 
 	malloc_active--;
@@ -1595,6 +1661,8 @@ posix_memalign(void **memptr, size_t alignment, size_t size)
 		malloc_recurse();
 		goto err;
 	}
+	if (size > 0 && size <= MALLOC_MAXCHUNK)
+		size += mopts.malloc_canaries;
 	r = omemalign(alignment, size, 0, CALLER);
 	malloc_active--;
 	_MALLOC_UNLOCK();