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==5061==ERROR: AddressSanitizer: stack-buffer-overflow on address 0xf0efc230033a at pc 0xf0efc4485124 bp 0xffffee420bd0 sp 0xffffee4203b0
WRITE of size 300 at 0xf0efc230033a thread T0
    #0 0xf0efc4485120 in memcpy ../../../../src/libsanitizer/sanitizer_common/sanitizer_common_interceptors_memintrinsics.inc:115
    #1 0xc484c5001134 in build_txt_record src/dns.c:390
    #2 0xc484c5002814 in handle_mdns_query src/dns.c:496
    #3 0xc484c5003aa8 in handle_mdns_record src/dns.c:575
    #4 0xc484c5003b78 in mdns_cb src/dns.c:584
    #5 0xc484c5003e98 in mg_call src/event.c:21
    #6 0xc484c5039378 in iolog src/sock.c:133
    #7 0xc484c503b68c in read_conn src/sock.c:362
    #8 0xc484c50406b4 in mg_mgr_poll src/sock.c:783
    #9 0xc484c504cc20 in main /data/pruva/runs/17a15ce6-4969-4882-9c55-0a227b0d8ef1/mongoose/tutorials/udp/mdns-sd-server/test_vuln.c:37
    #10 0xf0efc42084c0  (/lib/aarch64-linux-gnu/libc.so.6+0x284c0) (BuildId: d6c205bda1b6e91815f8fef45bdf56bc2239c37e)
    #11 0xf0efc4208594 in __libc_start_main (/lib/aarch64-linux-gnu/libc.so.6+0x28594) (BuildId: d6c205bda1b6e91815f8fef45bdf56bc2239c37e)
    #12 0xc484c4ffb1ac in _start (/data/pruva/runs/17a15ce6-4969-4882-9c55-0a227b0d8ef1/logs/test_vuln+0xb1ac) (BuildId: 37daaf260fa14a79b1d8c1f1a88d83f83f542357)

Address 0xf0efc230033a is located in stack of thread T0 at offset 826 in frame
    #0 0xc484c50011d0 in handle_mdns_query src/dns.c:396

  This frame has 7 object(s):
    [32, 34) 'offset' (line 480)
    [48, 50) 'offset' (line 506)
    [64, 72) 'rr' (line 398)
    [96, 112) 'defname' (line 411)
    [128, 192) 'req' (line 413)
    [224, 480) 'name' (line 408)
    [544, 826) 'buf' (line 405) <== Memory access at offset 826 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow ../../../../src/libsanitizer/sanitizer_common/sanitizer_common_interceptors_memintrinsics.inc:115 in memcpy
Shadow bytes around the buggy address:
  0xf0efc2300080: 00 00 00 00 00 00 00 00 f2 f2 f2 f2 00 00 00 00
  0xf0efc2300100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0xf0efc2300180: 00 00 00 00 00 00 00 00 00 00 00 00 f2 f2 f2 f2
  0xf0efc2300200: f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00
  0xf0efc2300280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0xf0efc2300300: 00 00 00 00 00 00 00[02]f3 f3 f3 f3 f3 f3 f3 f3
  0xf0efc2300380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0xf0efc2300400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0xf0efc2300480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0xf0efc2300500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0xf0efc2300580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==5061==ABORTING