[Bug 1912065] Re: Segfaults in tcg/optimize.c:212 after commit 7c79721606be11b5bc556449e5bcbc331ef6867d

[Richard Henderson]

** Changed in: qemu
       Status: In Progress => Fix Committed

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Title:
  Segfaults in tcg/optimize.c:212 after commit
  7c79721606be11b5bc556449e5bcbc331ef6867d

Status in QEMU:
  Fix Committed

Bug description:
  QEMU segfaults to NULL dereference in tcg/optimize.c:212 semi-randomly
  after commit 7c79721606be11b5bc556449e5bcbc331ef6867d

  Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
  Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000020
  Exception Note:        EXC_CORPSE_NOTIFY

  ...

  Thread 4 Crashed:
  0   qemu-system-ppc                   0x0000000109cd26d2 tcg_opt_gen_mov + 
178 (optimize.c:212)
  1   qemu-system-ppc                   0x0000000109ccf838 tcg_optimize + 5656
  2   qemu-system-ppc                   0x0000000109c27600 tcg_gen_code + 64 
(tcg.c:4490)
  3   qemu-system-ppc                   0x0000000109c17b6d tb_gen_code + 493 
(translate-all.c:1952)
  4   qemu-system-ppc                   0x0000000109c16085 tb_find + 41 
(cpu-exec.c:454) [inlined]
  5   qemu-system-ppc                   0x0000000109c16085 cpu_exec + 2117 
(cpu-exec.c:810)
  6   qemu-system-ppc                   0x0000000109c09ac3 tcg_cpus_exec + 35 
(tcg-cpus.c:57)
  7   qemu-system-ppc                   0x0000000109c75edd rr_cpu_thread_fn + 
445 (tcg-cpus-rr.c:217)
  8   qemu-system-ppc                   0x0000000109e41fae qemu_thread_start + 
126 (qemu-thread-posix.c:521)
  9   libsystem_pthread.dylib           0x00007fff2038e950 _pthread_start + 224
  10  libsystem_pthread.dylib           0x00007fff2038a47b thread_start + 15

  Here the crash is in tcg/optimize.c line 212:

    mask = si->mask;

  "si" is NULL. The NULL value arises from tcg/optimize.c line 198:

   si = ts_info(src_ts);

  I did not attempt to determine the root cause of this issue, however.
  It clearly is related to the "tcg/optimize" changes in this commit.
  The previous commit c0dd6654f207810b16a75b673258f5ce2ceffbf0 doesn't
  crash.

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