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  1. MariaDB Server
  2. MDEV-30613

output_core_info crashes in my_read()




      Seen in 10.4, possibly present elsewhere, did not check


      gcol.innodb_virtual_fk_restart 'innodb'  w13 [ fail ]  Found warnings/errors in server log file!
              Test ended at 2023-02-08 11:04:48
      ==213377==ERROR: LeakSanitizer: detected memory leaks
      SUMMARY: AddressSanitizer: 608 byte(s) leaked in 6 allocation(s).
      Attempting backtrace. You can use the following information to find out
      ^ Found warnings in /buildbot/amd64-ubuntu-1804-clang10-asan/build/mysql-test/var/13/log/mysqld.1.err
       - found 'core' (0/1)
      Core generated by '/buildbot/amd64-ubuntu-1804-clang10-asan/build/sql/mysqld'
      Output from gdb follows. The first stack trace is from the failing thread.
      The following stack traces are from all threads (so the failing one is
      [New LWP 213377]
      [Thread debugging using libthread_db enabled]
      Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
      Core was generated by `/buildbot/amd64-ubuntu-1804-clang10-asan/build/sql/mysqld --defaults-group-suff'.
      Program terminated with signal SIGSEGV, Segmentation fault.
      #0  0x00007fd47f54c2a7 in kill () from /lib/x86_64-linux-gnu/libc.so.6
      #0  0x00007fd47f54c2a7 in kill () from /lib/x86_64-linux-gnu/libc.so.6
      #1  0x00000000011473b0 in handle_fatal_signal (sig=<optimized out>) at signal_handler.cc:380
      #2  <signal handler called>
      #3  0x000000000261acf7 in my_read (Filedes=4, Buffer=0x7fff855daaa0 "Limit", ' ' <repeats 21 times>, "Soft Limit", ' ' <repeats 11 times>, "Hard Limit", ' ' <repeats 11 times>, "Units     \nMax cpu time", ' ' <repeats 14 times>, "unlimited", ' ' <repeats 12 times>, "unlimited", ' ' <repeats 12 times>, "seconds   \nMax file size", ' ' <repeats 13 times>, "unlimited       "..., Count=4096, MyFlags=0) at my_read.c:63
      #4  0x00000000011472b2 in output_core_info () at signal_handler.cc:73
      #5  handle_fatal_signal (sig=<optimized out>) at signal_handler.cc:364
      #6  <signal handler called>
      #7  0x00007fd47f54bfb7 in raise () from /lib/x86_64-linux-gnu/libc.so.6
      #8  0x00007fd47f54d921 in abort () from /lib/x86_64-linux-gnu/libc.so.6
      #9  0x00000000007307f7 in __sanitizer::Abort() () at /home/brian/src/final/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp:155
      #10 0x000000000072f221 in __sanitizer::Die() () at /home/brian/src/final/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_termination.cpp:58
      #11 0x000000000073c228 in __lsan::HandleLeaks() () at /home/brian/src/final/llvm-project/compiler-rt/lib/lsan/lsan_common_linux.cpp:115
      #12 0x0000000000739991 in DoLeakCheck () at /home/brian/src/final/llvm-project/compiler-rt/lib/lsan/lsan_common.cpp:614
      #13 0x00007fd47f550161 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
      #14 0x00007fd47f55025a in exit () from /lib/x86_64-linux-gnu/libc.so.6
      #15 0x0000000000748c6c in mysqld_exit (exit_code=0) at mysqld.cc:1964
      #16 0x0000000000750841 in mysqld_main (argc=<optimized out>, argv=0x646c6975622f0001) at mysqld.cc:5996
      #17 0x00007fd47f52ebf7 in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
      #18 0x000000000069a47a in _start ()

      The problem here is using my_read, which may accesses thread local storage variables and can dereference null pointer, if variables are not initialized

      for example, the innocuously looking line

            int got_errno= my_errno= errno;

      in my_read() potentially dereferences null pointer, since my_errno expands to my_thread_var->thr_errno, which in turn does my_pthread_getspecific() to get my_thread_var.

      I think the solution might be to abandon "my_" functions in error handler, an replace them with posix. unless one can rewrite the "my_" stuff in a safe manner, rather than assume existence of mysys thread local storage variable.


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              danblack Daniel Black
              wlad Vladislav Vaintroub
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