[Dnsmasq-discuss] Seg. fault in cache.c after commt b6f926fb

[Kristian Evensen]

Hello,

I recently updated one of my x86-based OpenWRT-routers to the latest
nightly, which bumped dnsmasq to 2.80test6. After the update, I see
that dnsmasq sometimes enters a crash loop. The crash occurs right
startup (SIGSEV), and the backtrace, looks as follows:

0x0000000000406a78 in make_non_terminals
(source=source at entry=0x7ffff7ffefa0) at cache.c:1437
1437 cache.c: No such file or directory.
(gdb) bt
#0  0x0000000000406a78 in make_non_terminals
(source=source at entry=0x7ffff7ffefa0) at cache.c:1437
#1  0x0000000000407192 in add_hosts_entry (cache=0x7ffff7ffefa0,
addr=0x7fffffffea28, addrlen=4, index=2, rhash=<optimized out>,
hashsz=<optimized out>) at cache.c:911
#2  0x00000000004074e1 in read_hostsfile
(filename=filename at entry=0x425a8a "/etc/hosts", index=index at entry=2,
cache_size=cache_size at entry=150, rhash=0x635020,
hashsz=hashsz at entry=641) at cache.c:1040
#3  0x0000000000407810 in cache_reload () at cache.c:1185
#4  0x0000000000418037 in clear_cache_and_reload
(now=now at entry=1537265437) at dnsmasq.c:1547
#5  0x0000000000405ec3 in async_event (now=1537265437, pipe=15) at
dnsmasq.c:1310
#6  main (argc=<optimized out>, argv=<optimized out>) at dnsmasq.c:1077

My current work-around is to check if crecp is NULL and then return
from make_non_terminals(). However, I don't know the code well enough
to know if this change will break anything else (though everything
seems to work fine).

There is nothing special with my hosts file, it looks as follows:

127.0.0.1 localhost

::1     localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
192.168.5.1 myrouter.lan

If checking for NULL is acceptable, I will be more than happy to send
my patch. If not, I wonder if anyone has any hints on how to proceed
to solve this issue?

BR,
Kristian