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From: Alexander Bulekov <alxndr@bu.edu>
To: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
Cc: Eduardo Habkost <ehabkost@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
	Richard Henderson <rth@twiddle.net>
Subject: Re: [RFC PATCH v2] hw/i386/vmport: Allow QTest use without crashing
Date: Sat, 23 May 2020 22:22:36 -0400
Message-ID: <20200524022230.rij2ehcmerhoj3ur@mozz.bu.edu> (raw)
In-Reply-To: <20200518103113.9882-1-f4bug@amsat.org>

On 200518 1231, Philippe Mathieu-Daudé wrote:
> Trying libFuzzer on the vmport device, we get:
>   AddressSanitizer:DEADLYSIGNAL
>   =================================================================
>   ==29476==ERROR: AddressSanitizer: SEGV on unknown address 0x000000008840 (pc 0x56448bec4d79 bp 0x7ffeec9741b0 sp 0x7ffeec9740e0 T0)
>   ==29476==The signal is caused by a READ memory access.
>     #0 0x56448bec4d78 in vmport_ioport_read (qemu-fuzz-i386+0x1260d78)
>     #1 0x56448bb5f175 in memory_region_read_accessor (qemu-fuzz-i386+0xefb175)
>     #2 0x56448bb30c13 in access_with_adjusted_size (qemu-fuzz-i386+0xeccc13)
>     #3 0x56448bb2ea27 in memory_region_dispatch_read1 (qemu-fuzz-i386+0xecaa27)
>     #4 0x56448bb2e443 in memory_region_dispatch_read (qemu-fuzz-i386+0xeca443)
>     #5 0x56448b961ab1 in flatview_read_continue (qemu-fuzz-i386+0xcfdab1)
>     #6 0x56448b96336d in flatview_read (qemu-fuzz-i386+0xcff36d)
>     #7 0x56448b962ec4 in address_space_read_full (qemu-fuzz-i386+0xcfeec4)
> X86CPU is NULL because QTest accelerator does not use CPU.
> Fix by returning default values when QTest accelerator is used.

Ah - it was QTest. Thank you for this - I would always run into this
crash within a second of fuzzing.

      parent reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-18 10:31 Philippe Mathieu-Daudé
2020-05-21 15:54 ` Paolo Bonzini
2020-05-24  2:22 ` Alexander Bulekov [this message]

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