[Bug 1919036] Re: Assertion failure in fifo8_push_all() through am53c974

[Mark Cave-Ayland]

Thanks for the test case - looks like the problem occurs because a
command hasn't been submitted before initiating a DMA transfer, and TC
is set to a value higher than the size of cmdfifo. Can you confirm that
the following fix works for you?

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 507ab363bc..0a26ee1dfd 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -573,6 +573,7 @@ static void esp_do_dma(ESPState *s)
         cmdlen = fifo8_num_used(&s->cmdfifo);
         trace_esp_do_dma(cmdlen, len);
         if (s->dma_memory_read) {
+            len = MIN(len, fifo8_num_free(&s->cmdfifo));
             s->dma_memory_read(s->dma_opaque, buf, len);
             fifo8_push_all(&s->cmdfifo, buf, len);
         } else {


ATB,

Mark.

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https://bugs.launchpad.net/bugs/1919036

Title:
  Assertion failure in fifo8_push_all() 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:43: fifo8_push_all: Assertion `fifo->num + 
num <= fifo->capacity' 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=0x555558ed2400 
"fifo->num + num <= fifo->capacity", file=file@entry=0x555558ed2380 
"../util/fifo8.c", line=line@entry=0x2b, function=function@entry=0x555558ed2560 
<__PRETTY_FUNCTION__.16583> "fifo8_push_all")
      at assert.c:92
  #3  0x00007ffff020a502 in __GI___assert_fail 
(assertion=assertion@entry=0x555558ed2400 "fifo->num + num <= fifo->capacity", 
file=file@entry=0x555558ed2380 "../util/fifo8.c", line=line@entry=0x2b, 
function=function@entry=0x555558ed2560 <__PRETTY_FUNCTION__.16583> 
"fifo8_push_all") at assert.c:101
  #4  0x00005555587749c4 in fifo8_push_all (fifo=fifo@entry=0x61f000005200, 
data=data@entry=0x7fff72bfa640 "", num=num@entry=0x24) at ../util/fifo8.c:43
  #5  0x00005555572bd13e in esp_do_dma (s=s@entry=0x61f000005088) at 
../hw/scsi/esp.c:577
  #6  0x00005555572bfc8f in handle_ti (s=0x61f000005088) at ../hw/scsi/esp.c:845
  #7  0x00005555572c419c in esp_reg_write (s=0x61f000005088, 
saddr=saddr@entry=0x3, val=<optimized out>)
      at ../hw/scsi/esp.c:987
  #8  0x0000555557bb916a in esp_pci_io_write (opaque=0x61f000004680, 
addr=<optimized out>, val=<optimized out>, size=<optimized out>) at 
../hw/scsi/esp-pci.c:214
  #9  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
  #10 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
  #11 0x00005555581892aa in memory_region_dispatch_write 
(mr=mr@entry=0x61f000004f70, addr=<optimized out>, data=<optimized out>, 
data@entry=0xffffff90, op=op@entry=MO_8, attrs=..., attrs@entry=...) at 
../softmmu/memory.c:1508
  #12 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
  #13 0x00007fff9323641c in code_gen_buffer ()
  #14 0x0000555557e793bb in cpu_tb_exec (tb_exit=<optimized out>, 
itb=<optimized out>, cpu=0x62e0000004b4)
      at ../accel/tcg/cpu-exec.c:190
  #15 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
  #16 0x0000555557e793bb in cpu_exec (cpu=cpu@entry=0x62e000000400) at 
../accel/tcg/cpu-exec.c:798
  #17 0x0000555557f5fc5a in tcg_cpus_exec (cpu=cpu@entry=0x62e000000400) at 
../accel/tcg/tcg-accel-ops.c:68
  #18 0x00005555582260af in mttcg_cpu_thread_fn (arg=arg@entry=0x62e000000400) 
at ../accel/tcg/tcg-accel-ops-mttcg.c:70
  #19 0x0000555558777b05 in qemu_thread_start (args=<optimized out>) at 
../util/qemu-thread-posix.c:521
  #20 0x00007ffff05d26db in start_thread (arg=0x7fff72bff700) at 
pthread_create.c:463
  #21 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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