[Bug 1919035] Re: Assertion failure in fifo8_pop_buf() through am53c974

[Alexander Bulekov]

QTest reproducer:

/*
 * Autogenerated Fuzzer Test Case
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or
 * later. See the COPYING file in the top-level directory.
 */

#include "qemu/osdep.h"

#include "libqos/libqtest.h"

/*
 * cat << EOF | ./qemu-system-i386 -display none -machine accel=qtest, \
 * -m 4G -device am53c974,id=scsi -device scsi-hd,drive=disk0 -drive \
 * id=disk0,if=none,file=null-co://,format=raw -nodefaults -qtest stdio
 * outl 0xcf8 0x80001004
 * outw 0xcfc 0x01
 * outl 0xcf8 0x8000100e
 * outl 0xcfc 0x8a000000
 * outl 0x8a09 0x42000000
 * outl 0x8a0d 0x00
 * outl 0x8a0b 0x1000
 * EOF
 */
static void test_fuzz(void)
{
    QTestState *s = qtest_init(
        "-display none , -m 4G -device am53c974,id=scsi -device "
        "scsi-hd,drive=disk0 -drive "
        "id=disk0,if=none,file=null-co://,format=raw -nodefaults");
    qtest_outl(s, 0xcf8, 0x80001004);
    qtest_outw(s, 0xcfc, 0x01);
    qtest_outl(s, 0xcf8, 0x8000100e);
    qtest_outl(s, 0xcfc, 0x8a000000);
    qtest_outl(s, 0x8a09, 0x42000000);
    qtest_outl(s, 0x8a0d, 0x00);
    qtest_outl(s, 0x8a0b, 0x1000);
    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/test_fuzz", test_fuzz);
    }

    return g_test_run();
}

-- 
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https://bugs.launchpad.net/bugs/1919035

Title:
  Assertion failure in fifo8_pop_buf() through am53c974

Status in QEMU:
  New

Bug description:
  Hello,

  Using hypervisor fuzzer, hyfuzz, I found an assertion failure through
  am53c974 emulator.

  A malicious guest user/process could use this flaw to abort the QEMU
  process on the host, resulting in a denial of service.

  This was found in version 5.2.0 (master, 3f8d1885e4)

  
  ```
  qemu-system-i386: ../util/fifo8.c:73: fifo8_pop_buf: Assertion `max > 0 && 
max <= fifo->num' failed.

  #0  0x00007ffff0218fb7 in __GI_raise (sig=sig@entry=0x6) at 
../sysdeps/unix/sysv/linux/raise.c:51
  #1  0x00007ffff021a921 in __GI_abort () at abort.c:79
  #2  0x00007ffff020a48a in __assert_fail_base (fmt=0x7ffff0391750 "%s%s%s:%u: 
%s%sAssertion `%s' failed.\n%n", assertion=assertion@entry=0x555558ed24a0 "max 
> 0 && max <= fifo->num", file=file@entry=0x555558ed2380 "../util/fifo8.c", 
line=line@entry=0x49, function=function@entry=0x555558ed24e0 
<__PRETTY_FUNCTION__.16603> "fifo8_pop_buf") at assert.c:92
  #3  0x00007ffff020a502 in __GI___assert_fail 
(assertion=assertion@entry=0x555558ed24a0 "max > 0 && max <= fifo->num", 
file=file@entry=0x555558ed2380 "../util/fifo8.c", line=line@entry=0x49, 
function=function@entry=0x555558ed24e0 <__PRETTY_FUNCTION__.16603> 
"fifo8_pop_buf") at assert.c:101
  #4  0x000055555877519a in fifo8_pop_buf (fifo=fifo@entry=0x61f000005200, 
max=max@entry=0xff, num=num@entry=0x7fff72bfa550) at ../util/fifo8.c:73
  #5  0x00005555572b7d9a in do_cmd (s=s@entry=0x61f000005088) at 
../hw/scsi/esp.c:328
  #6  0x00005555572b879a in esp_do_nodma (s=s@entry=0x61f000005088) at 
../hw/scsi/esp.c:701
  #7  0x00005555572bfd79 in handle_ti (s=0x61f000005088) at ../hw/scsi/esp.c:848
  #8  0x00005555572c419c in esp_reg_write (s=0x61f000005088, 
saddr=saddr@entry=0x3, val=<optimized out>) at ../hw/scsi/esp.c:987
  #9  0x0000555557bb916a in esp_pci_io_write (opaque=0x61f000004680, 
addr=<optimized out>, val=<optimized out>, size=<optimized out>) at 
../hw/scsi/esp-pci.c:214
  #10 0x000055555817ea28 in memory_region_write_accessor (mr=0x61f000004f70, 
addr=<optimized out>, value=<optimized out>, size=<optimized out>, 
shift=<optimized out>, mask=<optimized out>, attrs=...) at 
../softmmu/memory.c:491
  #11 0x0000555558176671 in access_with_adjusted_size (addr=addr@entry=0xc, 
value=value@entry=0x7fff72bfb2a8, size=size@entry=0x1, 
access_size_min=<optimized out>, access_size_max=<optimized out>, access_fn=
      0x55555817e7c0 <memory_region_write_accessor>, mr=0x61f000004f70, 
attrs=...) at ../softmmu/memory.c:552
  #12 0x00005555581892aa in memory_region_dispatch_write 
(mr=mr@entry=0x61f000004f70, addr=<optimized out>, data=<optimized out>, 
data@entry=0x10, op=op@entry=MO_8, attrs=..., attrs@entry=...) at 
../softmmu/memory.c:1508
  #13 0x0000555558024b66 in address_space_stb (as=<optimized out>, 
addr=<optimized out>, val=<optimized out>, attrs=..., result=0x0) at 
/home/cwmyung/prj/hyfuzz/src/qemu-master/memory_ldst.c.inc:382
  #14 0x00007fff93236d3c in code_gen_buffer ()
  #15 0x0000555557e793bb in cpu_tb_exec (tb_exit=<optimized out>, 
itb=<optimized out>, cpu=0x62e0000004b4) at ../accel/tcg/cpu-exec.c:190
  #16 0x0000555557e793bb in cpu_loop_exec_tb (tb_exit=<optimized out>, 
last_tb=<optimized out>, tb=<optimized out>, cpu=0x62e0000004b4) at 
../accel/tcg/cpu-exec.c:673
  #17 0x0000555557e793bb in cpu_exec (cpu=cpu@entry=0x62e000000400) at 
../accel/tcg/cpu-exec.c:798
  #18 0x0000555557f5fc5a in tcg_cpus_exec (cpu=cpu@entry=0x62e000000400) at 
../accel/tcg/tcg-accel-ops.c:68
  #19 0x00005555582260af in mttcg_cpu_thread_fn (arg=arg@entry=0x62e000000400) 
at ../accel/tcg/tcg-accel-ops-mttcg.c:70
  #20 0x0000555558777b05 in qemu_thread_start (args=<optimized out>) at 
../util/qemu-thread-posix.c:521
  #21 0x00007ffff05d26db in start_thread (arg=0x7fff72bff700) at 
pthread_create.c:463
  #22 0x00007ffff02fb71f in clone () at 
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
  ```

  
  To reproduce the assertion failure, please run the QEMU with the following 
command line.

  ```

  $ ./qemu-system-i386 -m 512 -drive
  file=./hyfuzz.img,index=0,media=disk,format=raw -device
  am53c974,id=scsi -device scsi-hd,drive=SysDisk -drive
  id=SysDisk,if=none,file=./disk.img

  ```

  Please let me know if I can provide any further info.

  Thank you.

  - Cheolwoo, Myung (Seoul National University)

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