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.

diff --git a/src/server.c b/src/server.c
index a622e22bda0811d4784cb6a6ebdc1393024217d0..918294b2f4f98a054eeeecb0e5bf0a660f7e3c15 100644 (file)
--- 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.