Dear Simon, CC mailing list, today I've received a report of latest dnsmasq embedded into Pi-hole crashing when www.facebook.com is visited (but only when logged in). I was able to reproduce this myself after creating a (fake) account.
The hit/miss ratio is not 100% but it should be possible to trigger the crash within a couple of tries. I tried Google Chrome on Linux for reproducing the crash (the report was Chrome on Windows). For this test, I used only one upstream server: 8.8.8.8 A PCAP I recorded using dumpmask=0xFFFF is attached. When the SIGSEGV happens, it can happen in a few different but related code places, let me summarize the two location I found most often below: https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=blob;f=src/blockdata.c;h=444a03a6798fce5da839f199df4a9326ab17188a;hb=HEAD#l217 Thread 1 "pihole-FTL" received signal SIGSEGV, Segmentation fault. blockdata_retrieve (block=<optimized out>, len=13, data=0x556b98069ac0, data@entry=0x0) at /app/FTL/src/dnsmasq/blockdata.c:217 217 memcpy(d, b->key, blen); (gdb) where #0 blockdata_retrieve (block=<optimized out>, len=13, data=0x556b98069ac0, data@entry=0x0) at /app/FTL/src/dnsmasq/blockdata.c:217 #1 0x0000556b95cd2092 in answer_request (header=header@entry=0x556b9800e290, limit=limit@entry=0x556b9800e490 "", qlen=qlen@entry=31, local_addr=..., local_addr@entry=..., local_netmask=..., local_netmask@entry=..., now=now@entry=1693587354, ad_reqd=<optimized out>, do_bit=<optimized out>, have_pseudoheader=<optimized out>, stale=<optimized out>, filtered=<optimized out>) at /app/FTL/src/dnsmasq/rfc1035.c:2175 #2 0x0000556b95cac02d in receive_query (listen=listen@entry=0x556b98002d60, now=now@entry=1693587354) at /app/FTL/src/dnsmasq/forward.c:1921 #3 0x0000556b95c99b61 in check_dns_listeners (now=now@entry=1693587354) at /app/FTL/src/dnsmasq/dnsmasq.c:1864 #4 0x0000556b95c9bd2d in main_dnsmasq (argc=<optimized out>, argv=<optimized out>) at /app/FTL/src/dnsmasq/dnsmasq.c:1271 #5 0x0000556b95bfaf76 in main (argc=<optimized out>, argv=0x7ffff6ee9598) at /app/FTL/src/main.c:152 sometimes the crash happens in https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=blob;f=src/blockdata.c;h=444a03a6798fce5da839f199df4a9326ab17188a;hb=HEAD#l177 Thread 1 "pihole-FTL" received signal SIGSEGV, Segmentation fault. blockdata_free (blocks=0x3368023268020600) at /app/FTL/src/dnsmasq/blockdata.c:177 177 void blockdata_free(struct blockdata *blocks) (gdb) where #0 blockdata_free (blocks=0x3368023268020600) at /app/FTL/src/dnsmasq/blockdata.c:177 #1 0x0000560c710c9715 in cache_scan_free (name=name@entry=0x560c7272f6d0 "star.c10r.facebook.com", addr=addr@entry=0x7ffe4bdaa9a0, class=class@entry=1, now=now@entry=1693587879, flags=flags@entry=1082130440, target_crec=target_crec@entry=0x7ffe4bdaa870, target_uid=0x7ffe4bdaa86c) at /app/FTL/src/dnsmasq/cache.c:541 #2 0x0000560c710cd43e in really_insert (name=0x560c7272f6d0 "star.c10r.facebook.com", addr=0x7ffe4bdaa9a0, class=1, now=1693587879, ttl=60, flags=1082130440) at /app/FTL/src/dnsmasq/cache.c:657 #3 0x0000560c7110aa6e in extract_addresses (header=header@entry=0x560c7273f290, qlen=<optimized out>, name=0x560c7272f6d0 "star.c10r.facebook.com", now=now@entry=1693587879, ipsets=ipsets@entry=0x0, nftsets=nftsets@entry=0x0, is_sign=0, check_rebind=0, no_cache_dnssec=0, secure=0, doctored=0x7ffe4bdaaa9c) at /app/FTL/src/dnsmasq/rfc1035.c:921 #4 0x0000560c710e39b6 in process_reply (header=header@entry=0x560c7273f290, now=now@entry=1693587879, server=0x560c7273d6d0, n=<optimized out>, n@entry=157, check_rebind=0, no_cache=no_cache@entry=0, cache_secure=0, bogusanswer=0, ad_reqd=0, do_bit=0, added_pheader=128, query_source=0x560c7278e150, limit=0x560c7273f760 "", ede=<optimized out>) at /app/FTL/src/dnsmasq/forward.c:833 #5 0x0000560c710e86c0 in return_reply (now=now@entry=1693587879, forward=forward@entry=0x560c7278e150, header=header@entry=0x560c7273f290, n=157, n@entry=140730171042832, status=<optimized out>) at /app/FTL/src/dnsmasq/forward.c:1397 #6 0x0000560c710e8c70 in dnssec_validate (forward=forward@entry=0x560c7278e150, header=header@entry=0x560c7273f290, plen=140730171042832, status=<optimized out>, status@entry=524288, now=now@entry=1693587879) at /app/FTL/src/dnsmasq/forward.c:1109 #7 0x0000560c710e8c1a in dnssec_validate (forward=forward@entry=0x560c72731a70, header=header@entry=0x560c7273f290, plen=plen@entry=855, status=status@entry=524288, now=now@entry=1693587879) at /app/FTL/src/dnsmasq/forward.c:1124 #8 0x0000560c710e9674 in reply_query (fd=<optimized out>, now=now@entry=1693587879) at /app/FTL/src/dnsmasq/forward.c:1319 #9 0x0000560c710d5dff in check_dns_listeners (now=now@entry=1693587879) at /app/FTL/src/dnsmasq/dnsmasq.c:1836 #10 0x0000560c710d7d2d in main_dnsmasq (argc=<optimized out>, argv=<optimized out>) at /app/FTL/src/dnsmasq/dnsmasq.c:1271 #11 0x0000560c71036f76 in main (argc=<optimized out>, argv=0x7ffe4bdab088) at /app/FTL/src/main.c:152 Best, Dominik
chrome_fb.pcap
Description: application/vnd.tcpdump.pcap
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