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From 27bf90a14670283a899b96c56dd23f8413e0973e Mon Sep 17 00:00:00 2001
From: David Lamparter <equinox@opensourcerouting.org>
Date: Wed, 4 Jun 2014 00:59:01 +0200
Subject: [PATCH] bgpd: fix double free after extcommunity set (BZ#799)
The route-map extcommunity set code was incorrectly assuming that it
owns the intern'd struct ecommunity reference. In reality, the intern'd
reference belongs to bgp_update_receive() and we're not supposed to
touch it in the route-map code.
Instead, like all the other set commands, we use a on-heap but
non-intern'd ecommunity to set the new value. This is then either
intern'd in bgp_update_main/_rsclient() through bgp_attr_intern(), or
free'd through bgp_attr_flush().
This fixes Bugzilla #799, which is that bgpd otherwise crashes with a
double free. The ecommunity got unintern'd first in the route-map set
command, then in bgp_update_receive().
Debugged-by: Milan Kocian <milon@wq.cz>
Reported-by: Florian S <florian@herrenlohe.de>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
---
bgpd/bgp_routemap.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/bgpd/bgp_routemap.c b/bgpd/bgp_routemap.c
index eb5e80f..36d177d 100644
--- a/bgpd/bgp_routemap.c
+++ b/bgpd/bgp_routemap.c
@@ -1552,14 +1552,19 @@ route_set_ecommunity (void *rule, struct prefix *prefix,
old_ecom = (bgp_attr_extra_get (bgp_info->attr))->ecommunity;
if (old_ecom)
- new_ecom = ecommunity_merge (ecommunity_dup (old_ecom), ecom);
+ {
+ new_ecom = ecommunity_merge (ecommunity_dup (old_ecom), ecom);
+
+ /* old_ecom->refcnt = 1 => owned elsewhere, e.g. bgp_update_receive()
+ * ->refcnt = 0 => set by a previous route-map statement */
+ if (!old_ecom->refcnt)
+ ecommunity_free (&old_ecom);
+ }
else
new_ecom = ecommunity_dup (ecom);
- bgp_info->attr->extra->ecommunity = ecommunity_intern (new_ecom);
-
- if (old_ecom)
- ecommunity_unintern (&old_ecom);
+ /* will be intern()'d or attr_flush()'d by bgp_update_main() */
+ bgp_info->attr->extra->ecommunity = new_ecom;
bgp_info->attr->flag |= ATTR_FLAG_BIT (BGP_ATTR_EXT_COMMUNITIES);
}
--
2.0.1
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