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Bug Report：SmartDNS crashes due to misaligned memory access in fast_ping.c. #1779

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dqp10515 opened this issue Jul 17, 2024 · 3 comments
Open

Bug Report：SmartDNS crashes due to misaligned memory access in fast_ping.c. #1779

dqp10515 opened this issue Jul 17, 2024 · 3 comments

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@dqp10515
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Issue Description

SmartDNS crashes due to misaligned memory access in fast_ping.c.

System Information

  • SmartDNS Version: clone and built on 20240717 with master branch

Steps to Reproduce

  1. Compile SmartDNS with ASan: 
    CC=clang CFLAGS="-g -fsanitize=address,undefined -fno-omit-frame-pointer" LDFLAGS="-fsanitize=address,undefined" make clean
CC=clang CFLAGS="-g -fsanitize=address,undefined -fno-omit-frame-pointer" LDFLAGS="-fsanitize=address,undefined" make all -j
cd smartdns/src
CC=clang CFLAGS="-g -fsanitize=address,undefined -fno-omit-frame-pointer" LDFLAGS="-fsanitize=address,undefined" make clean
CC=clang CFLAGS="-g -fsanitize=address,undefined -fno-omit-frame-pointer" LDFLAGS="-fsanitize=address,undefined" make all -j
cd smartdns/test
CC=clang CFLAGS="-g -fsanitize=address,undefined -fno-omit-frame-pointer" LDFLAGS="-fsanitize=address,undefined" make clean
CC=clang CFLAGS="-g -fsanitize=address,undefined -fno-omit-frame-pointer" LDFLAGS="-fsanitize=address,undefined" make all V=1 -j
  2. Start SmartDNS using the following command:
smartdns/src/smartdns -c smartdns/etc/smartdns/smartdns.conf -f -x
  1. Observe the crash after some DNS requests are processed.

Logs

server side:

[2024-07-17 13:24:51,990][NOTICE][       smartdns.c:558 ] smartdns starting...(Copyright (C) Nick Peng <pymumu@gmail.com>, build: 1.20240714-2229 (Release46-5-g550d455-dirty))
[2024-07-17 13:24:51,993][ INFO][     dns_server.c:9013] bind ip :5555, type 0
[2024-07-17 13:24:51,993][ INFO][     dns_server.c:9332] IPV6 is not ready or speed check is disabled, disable IPV6 features
[2024-07-17 13:24:51,994][ INFO][     dns_server.c:9219] auto enable cache persist.
[2024-07-17 13:24:51,994][ INFO][      dns_cache.c:758 ] load cache file /var/cache/smartdns/smartdns.cache, total 7 records
[2024-07-17 13:24:51,994][ INFO][     dns_client.c:1273] add server 8.8.8.8:53, type: udp
[2024-07-17 13:24:52,017][ INFO][     dns_client.c:1273] add server 1.1.1.1:853, type: tls
[2024-07-17 13:24:52,021][ INFO][     dns_server.c:4503] result: www.baidu.com, client: 127.0.0.1, qtype: 1, id: 57399, group: default, time: 0ms
[2024-07-17 13:24:52,021][ INFO][     dns_client.c:4253] request: www.baidu.com, qtype: 1, id: 50380, group: default
[2024-07-17 13:24:52,029][FATAL][       smartdns.c:679 ] process exit with signal 6, code = -6, errno = 0, pid = 1116534, self = 1116534, pc = 0x2, addr = 0x110976, build(Jul 14 2024 22:29:30 x86_64)
[2024-07-17 13:24:52,029][FATAL][           util.c:1857] Stack:
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #01: 0x67215c print_stack() from smartdns/src/smartdns+0x27215c
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #02: 0x76c8fb () from smartdns/src/smartdns+0x36c8fb
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #03: 0x7fea052f83c0 () from /lib/x86_64-linux-gnu/libpthread.so.0+0x153c0
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #04: 0x7fea04fba18b gsignal() from /lib/x86_64-linux-gnu/libc.so.6+0x4618b
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #05: 0x7fea04f99859 abort() from /lib/x86_64-linux-gnu/libc.so.6+0x25859
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #06: 0x52058f () from smartdns/src/smartdns+0x12058f
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #07: 0x51d9fc () from smartdns/src/smartdns+0x11d9fc
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #08: 0x529d91 () from smartdns/src/smartdns+0x129d91
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #09: 0x52d16a () from smartdns/src/smartdns+0x12d16a
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #10: 0x52d525 __ubsan_handle_type_mismatch_v1() from smartdns/src/smartdns+0x12d525
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #11: 0x606864 () from smartdns/src/smartdns+0x206864
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #12: 0x604e00 () from smartdns/src/smartdns+0x204e00
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #13: 0x60067d () from smartdns/src/smartdns+0x20067d
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #14: 0x5fe6ab () from smartdns/src/smartdns+0x1fe6ab
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #15: 0x5ec319 () from smartdns/src/smartdns+0x1ec319
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #16: 0x7fea052ec609 () from /lib/x86_64-linux-gnu/libpthread.so.0+0x9609
[2024-07-17 13:24:52,029][FATAL][           util.c:1869] #17: 0x7fea05096293 clone() from /lib/x86_64-linux-gnu/libc.so.6+0x122293
[2024-07-17 13:24:52,030][ INFO][     dns_server.c:4503] result: baidu.com, client: 127.0.0.1, qtype: 28, id: 54161, group: default, time: 1ms
[2024-07-17 13:24:52,030][ INFO][     dns_client.c:4253] request: baidu.com, qtype: 28, id: 39730, group: default
[2024-07-17 13:24:52,038][ INFO][     dns_client.c:4253] request: www.baidu.com, qtype: 5, id: 11505, group: default
[2024-07-17 13:24:52,039][ INFO][     dns_server.c:4503] result: www.baidu.com, client: 127.0.0.1, qtype: 5, id: 29224, group: default, time: 1ms
[2024-07-17 13:24:52,047][ INFO][     dns_client.c:4253] request: www.baidu.com, qtype: 14, id: 55488, group: default
[2024-07-17 13:24:52,048][ INFO][     dns_server.c:4503] result: www.baidu.com, client: 127.0.0.1, qtype: 14, id: 6726, group: default, time: 1ms
[2024-07-17 13:24:52,056][ INFO][     dns_client.c:4253] request: www.baidu.com, qtype: 9, id: 36080, group: default
[2024-07-17 13:24:52,056][ INFO][     dns_server.c:4503] result: www.baidu.com, client: 127.0.0.1, qtype: 9, id: 2259, group: default, time: 1ms
[2024-07-17 13:24:52,065][ INFO][     dns_server.c:4503] result: ad.test.com, client: 127.0.0.1, qtype: 1, id: 24687, group: default, time: 0ms
[2024-07-17 13:24:52,065][ INFO][     dns_client.c:4253] request: ad.test.com, qtype: 1, id: 63765, group: default
[2024-07-17 13:24:52,073][ INFO][     dns_client.c:4253] request: test.com, qtype: 2, id: 16444, group: default
[2024-07-17 13:24:52,074][ INFO][     dns_server.c:4503] result: test.com, client: 127.0.0.1, qtype: 2, id: 55919, group: default, time: 1ms
[2024-07-17 13:24:52,082][ INFO][     dns_server.c:4503] result: ad.test.org, client: 127.0.0.1, qtype: 1, id: 59105, group: default, time: 0ms
[2024-07-17 13:24:52,082][ INFO][     dns_client.c:4253] request: ad.test.org, qtype: 1, id: 32156, group: default
[2024-07-17 13:24:52,097][ INFO][     dns_server.c:4503] result: thekelleys.org.uk, client: 127.0.0.1, qtype: 1, id: 11398, group: default, time: 0ms
[2024-07-17 13:24:52,097][ INFO][     dns_client.c:4253] request: thekelleys.org.uk, qtype: 1, id: 5414, group: default
[2024-07-17 13:24:52,105][ INFO][     dns_client.c:4253] request: thekelleys.org.uk, qtype: 13, id: 25378, group: default
[2024-07-17 13:24:52,106][ INFO][     dns_server.c:4503] result: thekelleys.org.uk, client: 127.0.0.1, qtype: 13, id: 33162, group: default, time: 1ms
[2024-07-17 13:24:52,113][ INFO][     dns_client.c:4253] request: thekelleys.org.uk, qtype: 7, id: 34166, group: default
[2024-07-17 13:24:52,594][ INFO][     dns_server.c:1235] result: ad.test.org, qtype: 1, rtcode: 3, id: 0
[2024-07-17 13:24:52,714][ INFO][     dns_server.c:4503] result: thekelleys.org.uk, client: 127.0.0.1, qtype: 7, id: 65432, group: default, time: 600ms

ASan report:

fast_ping.c:1598:18: runtime error: member access within misaligned address 0x7fe9fe58a034 for type 'struct fast_ping_packet', which requires 8 byte alignment
0x7fe9fe58a034: note: pointer points here
  ac 11 00 05 00 00 0f 20  76 09 00 01 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
    #0 0x606863  (smartdns/src/smartdns+0x606863)
    #1 0x604dff  (smartdns/src/smartdns+0x604dff)
    #2 0x60067c  (smartdns/src/smartdns+0x60067c)
    #3 0x5fe6aa  (smartdns/src/smartdns+0x5fe6aa)
    #4 0x5ec318  (smartdns/src/smartdns+0x5ec318)
    #5 0x7fea052ec608  (/lib/x86_64-linux-gnu/libpthread.so.0+0x9608)
    #6 0x7fea05096292  (/lib/x86_64-linux-gnu/libc.so.6+0x122292)

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior fast_ping.c:1598:18 in
@pymumu
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pymumu commented Jul 18, 2024

The smartdns code currently does not strictly adhere to byte alignment, which may lead to degraded performance or exceptions on certain architectures during runtime.

In what situations is byte alignment required?

@pymumu
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pymumu commented Jul 20, 2024

Please check the latest code.

@dqp10515
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Thank you for updating the code.

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@pymumu @dqp10515