From: Claudio Jeker <cjeker@diehard.n-r-g.com>
Subject: bgpd: other attributes vs the bucket allocator
To: tech@openbsd.org
Date: Thu, 30 Apr 2026 21:22:56 +0200

This is a fun one. The new bucket allocator used for attrs jumps from
240 to 256 entries. The problem is that l is a uint8_t and so 256
becomes 0. The reallocarray shrinks the array and you can imagine the
rest.

In attr_optadd() check the value returned by bin_of_attrs() and limit it
to UCHAR_MAX to prevent the overflow. Also switch the iterator variable
from uint8_t to int (I did this everywhere because it is more natural).

Does this make sense?
-- 
:wq Claudio

Index: mrt.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/mrt.c,v
diff -u -p -r1.134 mrt.c
--- mrt.c	17 Feb 2026 14:06:44 -0000	1.134
+++ mrt.c	30 Apr 2026 18:35:08 -0000
@@ -222,9 +222,9 @@ mrt_attr_dump(struct ibuf *buf, struct r
 	struct attr	*oa;
 	u_char		*pdata;
 	uint32_t	 tmp;
-	int		 neednewpath = 0;
+	int		 l, neednewpath = 0;
 	uint16_t	 plen, afi;
-	uint8_t		 l, safi;
+	uint8_t		 safi;
 
 	/* origin */
 	if (attr_writebuf(buf, ATTR_WELL_KNOWN, ATTR_ORIGIN,
Index: rde.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/rde.c,v
diff -u -p -r1.694 rde.c
--- rde.c	27 Apr 2026 15:52:20 -0000	1.694
+++ rde.c	30 Apr 2026 19:00:49 -0000
@@ -2924,7 +2924,7 @@ rde_dump_rib_as(struct prefix *p, struct
 	struct rde_peer		*peer;
 	monotime_t		 staletime;
 	size_t			 aslen;
-	uint8_t			 l;
+	int			 l;
 
 	nexthop = prefix_nexthop(p);
 	peer = prefix_peer(p);
@@ -3042,7 +3042,7 @@ rde_dump_adjout_as(struct rde_peer *peer
 	struct rde_aspath	*asp;
 	struct nexthop		*nexthop;
 	size_t			 aslen;
-	uint8_t			 l;
+	int			 l;
 
 	nexthop = attrs->nexthop;
 	asp = attrs->aspath;
Index: rde_attr.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/rde_attr.c,v
diff -u -p -r1.141 rde_attr.c
--- rde_attr.c	17 Mar 2026 09:29:29 -0000	1.141
+++ rde_attr.c	30 Apr 2026 19:08:36 -0000
@@ -95,7 +95,7 @@ int
 attr_optadd(struct rde_aspath *asp, uint8_t flags, uint8_t type,
     void *data, uint16_t len)
 {
-	uint8_t		 l;
+	int		 l;
 	struct attr	*a, *t;
 	struct attr	**p;
 	uint64_t	 h;
@@ -137,6 +137,8 @@ attr_optadd(struct rde_aspath *asp, uint
 		fatalx("attr_optadd: attribute overflow");
 
 	l = bin_of_attrs(asp->others_len + 1);
+	if (l > UCHAR_MAX)
+		l = UCHAR_MAX;
 	if ((p = reallocarray(asp->others, l, sizeof(struct attr *))) == NULL)
 		fatal("%s", __func__);
 	memset(&p[asp->others_len], 0, (l - asp->others_len) * sizeof(*p));
@@ -150,7 +152,7 @@ attr_optadd(struct rde_aspath *asp, uint
 struct attr *
 attr_optget(const struct rde_aspath *asp, uint8_t type)
 {
-	uint8_t l;
+	int l;
 
 	for (l = 0; l < asp->others_len; l++) {
 		if (asp->others[l] == NULL)
@@ -166,7 +168,7 @@ attr_optget(const struct rde_aspath *asp
 void
 attr_copy(struct rde_aspath *t, const struct rde_aspath *s)
 {
-	uint8_t l;
+	int l;
 
 	if (t->others != NULL)
 		attr_freeall(t);
@@ -206,7 +208,7 @@ attr_eq(const struct attr *oa, const str
 int
 attr_equal(const struct rde_aspath *a, const struct rde_aspath *b)
 {
-	uint8_t l;
+	int l;
 
 	if (a->others_len != b->others_len)
 		return (0);
@@ -219,7 +221,7 @@ attr_equal(const struct rde_aspath *a, c
 void
 attr_free(struct rde_aspath *asp, struct attr *attr)
 {
-	uint8_t l;
+	int l;
 
 	for (l = 0; l < asp->others_len; l++)
 		if (asp->others[l] == attr) {
@@ -236,7 +238,7 @@ attr_free(struct rde_aspath *asp, struct
 void
 attr_freeall(struct rde_aspath *asp)
 {
-	uint8_t l;
+	int l;
 
 	for (l = 0; l < asp->others_len; l++)
 		attr_put(asp->others[l]);
Index: rde_update.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/rde_update.c,v
diff -u -p -r1.193 rde_update.c
--- rde_update.c	11 Feb 2026 10:24:57 -0000	1.193
+++ rde_update.c	30 Apr 2026 18:36:05 -0000
@@ -591,9 +591,9 @@ up_generate_attr(struct ibuf *buf, struc
 	struct attr	*oa = NULL, *newaggr = NULL;
 	u_char		*pdata;
 	uint32_t	 tmp32;
-	int		 flags, neednewpath = 0, rv;
+	int		 flags, neednewpath = 0, rv, oalen = 0;
 	uint16_t	 plen;
-	uint8_t		 oalen = 0, type;
+	uint8_t		 type;
 
 	if (asp->others_len > 0)
 		oa = asp->others[oalen++];