Hi, this is a patch for issue #775.
-- Jérôme
>From 68e8b71c50d0805faf5facba587f1c8c3f1760b7 Mon Sep 17 00:00:00 2001 From: Jerome Magnin <jer...@layaute.net> Date: Tue, 28 Jul 2020 13:38:22 +0200 Subject: [PATCH] BUG/MAJOR: dns: fix null pointer dereference in snr_update_srv_status Since commit 13a9232eb ("MEDIUM: dns: use Additional records from SRV responses"), a struct server can have a NULL dns_requester->resolution, when SRV records are used and DNS answers contain an Additional section. This is a problem when we call snr_update_srv_status() because it does not check that resolution is NULL, and dereferences it. This patch simply adds a test for resolution being NULL. When that happens, it means we are using SRV records with Additional records, and an entry was removed. This should fix issue #775. This should be backported to 2.2. --- src/server.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/server.c b/src/server.c index a622e22bd..918294b2f 100644 --- a/src/server.c +++ b/src/server.c @@ -3731,6 +3731,15 @@ int snr_update_srv_status(struct server *s, int has_no_ip) struct dns_resolution *resolution = s->dns_requester->resolution; int exp; + /* If resolution is NULL we're dealing with SRV records Additional records */ + if (resolution == NULL) { + if (s->next_admin & SRV_ADMF_RMAINT) + return 1; + + srv_set_admin_flag(s, SRV_ADMF_RMAINT, "entry removed from SRV record"); + return 0; + } + switch (resolution->status) { case RSLV_STATUS_NONE: /* status when HAProxy has just (re)started. -- 2.27.0