qemu-system-i386 virtio-vga: Assertion in address_space_stw_le_cached failed again

[Qiuhao Li]

When I was fuzzing virtio-vga device of the latest QEMU (1758428, Dec 12, built with --enable-sanitizers --enable-fuzzing), an assertion failed in include/exec/memory_ldst_cached.h.inc.

--[ Reproducer

cat << EOF | ./build/i386-softmmu/qemu-system-i386 -machine accel=qtest \
-machine q35 -display none -nodefaults -device virtio-vga -qtest stdio
outl 0xcf8 0x8000081c
outb 0xcfc 0xc3
outl 0xcf8 0x80000804
outb 0xcfc 0x06
write 0xc300001024 0x2 0x0040
write 0xc300001028 0x1 0x5a
write 0xc30000101c 0x1 0x01
writel 0xc30000100c 0x20000000
write 0xc300001016 0x3 0x80a080
write 0xc300003002 0x1 0x80
write 0x5c 0x1 0x10
EOF

--[ Output

==35337==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
[I 1607946348.442865] OPENED
[R +0.059305] outl 0xcf8 0x8000081c
OK
[S +0.059326] OK
[R +0.059338] outb 0xcfc 0xc3
OK
[S +0.059355] OK
[R +0.059363] outl 0xcf8 0x80000804
OK
[S +0.059369] OK
[R +0.059381] outb 0xcfc 0x06
OK
[S +0.061094] OK
[R +0.061107] write 0xc300001024 0x2 0x0040
OK
[S +0.061120] OK
[R +0.061127] write 0xc300001028 0x1 0x5a
OK
[S +0.061135] OK
[R +0.061142] write 0xc30000101c 0x1 0x01
OK
[S +0.061158] OK
[R +0.061167] writel 0xc30000100c 0x20000000
OK
[S +0.061212] OK
[R +0.061222] write 0xc300001016 0x3 0x80a080
OK
[S +0.061231] OK
[R +0.061238] write 0xc300003002 0x1 0x80
OK
[S +0.061247] OK
[R +0.061253] write 0x5c 0x1 0x10
OK
[S +0.061403] OK
qemu-system-i386: /home/qiuhao/hack/qemu/include/exec/memory_ldst_cached.h.inc:88: void address_space_stw_le_cached(MemoryRegionCache *, hwaddr, uint32_t, MemTxAttrs, MemTxResult *): Assertion `addr < cache->len && 2 <= cache->len - addr' failed.

--[ Environment

Ubuntu 20.04.1 5.4.0-58-generic x86_64
clang: 10.0.0-4ubuntu1
glibc: 2.31-0ubuntu9.1
libglib2.0-dev: 2.64.3-1~ubuntu20.04.1

--[ Note

Alexander Bulekov found the same assertion failure on 2020-08-04, https://bugs.launchpad.net/qemu/+bug/1890333, and it had been fixed in commit 2d69eba5fe52045b2c8b0d04fd3806414352afc1.

Fam Zheng found the same assertion failure on 2018-09-29, https://bugs.launchpad.net/qemu/+bug/1795148, and it had been fixed in commit db812c4073c77c8a64db8d6663b3416a587c7b4a.

[Qiuhao Li (qiuhao)]

--[ Original Fuzzing output

./build/qemu-fuzz-i386 --fuzz-target=generic-fuzz-virtio-vga ../fuzz/20201208/crash-da778083c63d2b24d8f7780383b2602a7a156352

qemu-fuzz-i386: /home/qiuhao/hack/qemu/include/exec/memory_ldst_cached.h.inc:88: void address_space_stw_le_cached(MemoryRegionCache *, hwaddr, uint32_t, MemTxAttrs, MemTxResult *): Assertion `addr < cache->len && 2 <= cache->len - addr' failed.
==37260== ERROR: libFuzzer: deadly signal
    #0 0x56336c2ebc81 in __sanitizer_print_stack_trace (/home/qiuhao/hack/qemu/build/qemu-fuzz-i386+0x305dc81)
    #1 0x56336c236dd8 in fuzzer::PrintStackTrace() (/home/qiuhao/hack/qemu/build/qemu-fuzz-i386+0x2fa8dd8)
    #2 0x56336c21bf23 in fuzzer::Fuzzer::CrashCallback() (/home/qiuhao/hack/qemu/build/qemu-fuzz-i386+0x2f8df23)
    #3 0x7f3122f7b3bf (/lib/x86_64-linux-gnu/libpthread.so.0+0x153bf)
    #4 0x7f3122d8c18a in __libc_signal_restore_set /build/glibc-ZN95T4/glibc-2.31/signal/../sysdeps/unix/sysv/linux/internal-signals.h:86:3
    #5 0x7f3122d8c18a in raise /build/glibc-ZN95T4/glibc-2.31/signal/../sysdeps/unix/sysv/linux/raise.c:48:3
    #6 0x7f3122d6b858 in abort /build/glibc-ZN95T4/glibc-2.31/stdlib/abort.c:79:7
    #7 0x7f3122d6b728 in __assert_fail_base /build/glibc-ZN95T4/glibc-2.31/assert/assert.c:92:3
    #8 0x7f3122d7cf35 in __assert_fail /build/glibc-ZN95T4/glibc-2.31/assert/assert.c:101:3
    #9 0x56336ec7c8ab in address_space_stw_le_cached /home/qiuhao/hack/qemu/include/exec/memory_ldst_cached.h.inc:88:5
    #10 0x56336ec7b746 in stw_le_phys_cached /home/qiuhao/hack/qemu/include/exec/memory_ldst_phys.h.inc:121:5
    #11 0x56336ec7acf8 in virtio_stw_phys_cached /home/qiuhao/hack/qemu/include/hw/virtio/virtio-access.h:196:9
    #12 0x56336ec79f7b in vring_set_avail_event /home/qiuhao/hack/qemu/build/../hw/virtio/virtio.c:429:5
    #13 0x56336ec376f5 in virtqueue_split_pop /home/qiuhao/hack/qemu/build/../hw/virtio/virtio.c:1452:9
    #14 0x56336ec3131c in virtqueue_pop /home/qiuhao/hack/qemu/build/../hw/virtio/virtio.c:1695:16
    #15 0x56336c57fa43 in virtio_gpu_handle_ctrl /home/qiuhao/hack/qemu/build/../hw/display/virtio-gpu.c:877:11
    #16 0x56336c57f6d9 in virtio_gpu_ctrl_bh /home/qiuhao/hack/qemu/build/../hw/display/virtio-gpu.c:898:5
    #17 0x563370ad4952 in aio_bh_call /home/qiuhao/hack/qemu/build/../util/async.c:136:5
    #18 0x563370ad6352 in aio_bh_poll /home/qiuhao/hack/qemu/build/../util/async.c:164:13
    #19 0x563370a2773b in aio_dispatch /home/qiuhao/hack/qemu/build/../util/aio-posix.c:381:5
    #20 0x563370adfd5e in aio_ctx_dispatch /home/qiuhao/hack/qemu/build/../util/async.c:306:5
    #21 0x7f312319afbc in g_main_context_dispatch (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x51fbc)
    #22 0x563370942137 in glib_pollfds_poll /home/qiuhao/hack/qemu/build/../util/main-loop.c:221:9
    #23 0x56337093fa37 in os_host_main_loop_wait /home/qiuhao/hack/qemu/build/../util/main-loop.c:244:5
    #24 0x56337093f387 in main_loop_wait /home/qiuhao/hack/qemu/build/../util/main-loop.c:520:11
    #25 0x56336c33ec22 in flush_events /home/qiuhao/hack/qemu/build/../tests/qtest/fuzz/fuzz.c:49:9
    #26 0x56336c33311b in generic_fuzz /home/qiuhao/hack/qemu/build/../tests/qtest/fuzz/generic_fuzz.c:...

[Thomas Huth (th-huth)]

The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting the bug state to "Incomplete" now.

If the bug has already been fixed in the latest upstream version of QEMU,
then please close this ticket as "Fix released".

If it is not fixed yet and you think that this bug report here is still
valid, then you have two options:

1) If you already have an account on gitlab.com, please open a new ticket
for this problem in our new tracker here:

    https://gitlab.com/qemu-project/qemu/-/issues

and then close this ticket here on Launchpad (or let it expire auto-
matically after 60 days). Please mention the URL of this bug ticket on
Launchpad in the new ticket on GitLab.

2) If you don't have an account on gitlab.com and don't intend to get
one, but still would like to keep this ticket opened, then please switch
the state back to "New" or "Confirmed" within the next 60 days (other-
wise it will get closed as "Expired"). We will then eventually migrate
the ticket automatically to the new system (but you won't be the reporter
of the bug in the new system and thus you won't get notified on changes
anymore).

Thank you and sorry for the inconvenience.

[Thomas Huth (th-huth)]

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/300