[Bug 1918321] Re: [OSS-Fuzz] Issue 31875 megasas: Null-ptr dereference in megasas_finish_dcmd

[Thomas Huth]

Thanks for moving it over! ... let's close this one here on Launchpad
now.


** Changed in: qemu
       Status: Confirmed => Invalid

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Title:
  [OSS-Fuzz] Issue 31875 megasas: Null-ptr dereference in
  megasas_finish_dcmd

Status in QEMU:
  Invalid

Bug description:
  Hello,

  == QTest Reproducer ==
  /* 
   * cat << EOF | ./qemu-system-i386 -display none -machine accel=qtest, -m \
   * 512M -machine q35 -nodefaults -device megasas -device \
   * scsi-cd,drive=null0 -blockdev \
   * driver=null-co,read-zeroes=on,node-name=null0 -qtest stdio
   * outl 0xcf8 0x80000801
   * outl 0xcfc 0x05000000
   * outl 0xcf8 0x80000816
   * outl 0xcfc 0x19000000
   * write 0x1e1ed300 0x1 0x01
   * write 0x1e1ed307 0x1 0x01
   * write 0x1e1ed316 0x1 0x01
   * write 0x1e1ed328 0x1 0x01
   * write 0x1e1ed32f 0x1 0x01
   * outl 0x1940 0x1e1ed300
   * outl 0x19c0 0x00
   * EOF
   */
  static void null_deref_megasas_finish_dcmd(void)
  {
      QTestState *s = qtest_init(
          "-display none , -m 512M -machine q35 -nodefaults -device megasas 
-device "
          "scsi-cd,drive=null0 -blockdev 
driver=null-co,read-zeroes=on,node-name=null0 ");
      qtest_outl(s, 0xcf8, 0x80000801);
      qtest_outl(s, 0xcfc, 0x05000000);
      qtest_outl(s, 0xcf8, 0x80000816);
      qtest_outl(s, 0xcfc, 0x19000000);
      qtest_bufwrite(s, 0x1e1ed300, "\x01", 0x1);
      qtest_bufwrite(s, 0x1e1ed307, "\x01", 0x1);
      qtest_bufwrite(s, 0x1e1ed316, "\x01", 0x1);
      qtest_bufwrite(s, 0x1e1ed328, "\x01", 0x1);
      qtest_bufwrite(s, 0x1e1ed32f, "\x01", 0x1);
      qtest_outl(s, 0x1940, 0x1e1ed300);
      qtest_outl(s, 0x19c0, 0x00);
      qtest_quit(s);
  }
  int main(int argc, char **argv)
  {
      const char *arch = qtest_get_arch();

      g_test_init(&argc, &argv, NULL);

      if (strcmp(arch, "i386") == 0) {
          qtest_add_func("fuzz/null_deref_megasas_finish_dcmd",
                         null_deref_megasas_finish_dcmd);
      }

      return g_test_run();
  }

  == Stack Trace ==
  ../hw/scsi/megasas.c:1884:21: runtime error: member access within null 
pointer of type 'union mfi_frame'
  SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior 
../hw/scsi/megasas.c:1884:21 in
  ../hw/scsi/megasas.c:1884:21: runtime error: member access within null 
pointer of type 'struct mfi_frame_header'
  SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior 
../hw/scsi/megasas.c:1884:21 in
  AddressSanitizer:DEADLYSIGNAL
  =================================================================
  ==314546==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000003 (pc 
0x55b1b4f4de73 bp 0x7ffcfc5a8bb0 sp 0x7ffcfc5a8900 T0)
  ==314546==The signal is caused by a WRITE memory access.
  ==314546==Hint: address points to the zero page.
  #0 0x55b1b4f4de73 in megasas_command_complete 
build/../hw/scsi/megasas.c:1884:40
  #1 0x55b1b5613914 in scsi_req_complete build/../hw/scsi/scsi-bus.c:1515:5
  #2 0x55b1b5448aeb in scsi_dma_complete_noio build/../hw/scsi/scsi-disk.c:345:9
  #3 0x55b1b5446fc7 in scsi_dma_complete build/../hw/scsi/scsi-disk.c:366:5
  #4 0x55b1b4fffc56 in dma_complete build/../softmmu/dma-helpers.c:121:9
  #5 0x55b1b4fffc56 in dma_blk_cb build/../softmmu/dma-helpers.c:139:9
  #6 0x55b1b6856016 in blk_aio_complete build/../block/block-backend.c:1412:9
  #7 0x55b1b6f48b06 in aio_bh_poll build/../util/async.c:164:13
  #8 0x55b1b6f08cec in aio_dispatch build/../util/aio-posix.c:381:5
  #9 0x55b1b6f4d59c in aio_ctx_dispatch build/../util/async.c:306:5
  #10 0x7fd88c098baa in g_main_context_dispatch 
(/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x51baa)
  #11 0x55b1b6f59a3c in glib_pollfds_poll build/../util/main-loop.c:232:9
  #12 0x55b1b6f59a3c in os_host_main_loop_wait build/../util/main-loop.c:255:5
  #13 0x55b1b6f59a3c in main_loop_wait build/../util/main-loop.c:531:11
  #14 0x55b1b61a78a9 in qemu_main_loop build/../softmmu/runstate.c:725:9
  #15 0x55b1b4c751e5 in main build/../softmmu/main.c:50:5
  #16 0x7fd88aec6d09 in __libc_start_main csu/../csu/libc-start.c:308:16
  #17 0x55b1b4bc8bb9 in _start (system-i386+0x2b5fbb9)

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