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Re: [Bug 1878134] [NEW] Assertion failures in ati_reg_read_offs/ati_reg_
From: |
BALATON Zoltan |
Subject: |
Re: [Bug 1878134] [NEW] Assertion failures in ati_reg_read_offs/ati_reg_write_offs |
Date: |
Sat, 16 May 2020 11:25:17 -0000 |
On Fri, 15 May 2020, Launchpad Bug Tracker wrote:
> You have been subscribed to a public bug by Philippe Mathieu-Daudé (philmd):
>
> Hello,
> While fuzzing, I found inputs that trigger assertion failures in
> ati_reg_read_offs/ati_reg_write_offs
>
> uint32_t extract32(uint32_t, int, int): Assertion `start >= 0 && length
>> 0 && length <= 32 - start' failed
>
> #3 0x00007ffff6866092 in __GI___assert_fail (assertion=0x555556e760c0 <str>
> "start >= 0 && length > 0 && length <= 32 - start", file=0x555556e76120 <str>
> "/home/alxndr/Development/qemu/include/qemu/bitops.h", line=0x12c,
> function=0x555556e76180 <__PRETTY_FUNCTION__.extract32> "uint32_t
> extract32(uint32_t, int, int)") at assert.c:101
> #4 0x000055555653d8a7 in ati_mm_read (opaque=<optimized out>, addr=0x1a,
> size=<optimized out>) at
> /home/alxndr/Development/qemu/include/qemu/log-for-trace.h:29
> #5 0x000055555653c825 in ati_mm_read (opaque=<optimized out>, addr=0x4,
> size=<optimized out>) at /home/alxndr/Development/qemu/hw/display/ati.c:289
> #6 0x000055555601446e in memory_region_read_accessor (mr=0x63100004dc20,
> addr=<optimized out>, value=<optimized out>, size=<optimized out>,
> shift=<optimized out>, mask=<optimized out>, attrs=...) at
> /home/alxndr/Development/qemu/memory.c:434
> #7 0x0000555556001a70 in access_with_adjusted_size (addr=<optimized out>,
> value=<optimized out>, size=<optimized out>, access_size_min=<optimized out>,
> access_size_max=<optimized out>, access_fn=<optimized out>,
> mr=0x63100004dc20, attrs=...) at /home/alxndr/Development/qemu/memory.c:544
> #8 0x0000555556001a70 in memory_region_dispatch_read1 (mr=0x63100004dc20,
> addr=0x4, pval=<optimized out>, size=0x4, attrs=...) at
> /home/alxndr/Development/qemu/memory.c:1396
Here's a stack trace with --enable debug which is more useful:
#4 0x0000555555b39464 in extract32 (value=0, start=16, length=32) at
/home/balaton/src/qemu/include/qemu/bitops.h:300
#5 0x0000555555b3a45f in ati_reg_read_offs (reg=0, offs=2, size=4) at
hw/display/ati.c:269
#6 0x0000555555b3a9f1 in ati_mm_read (opaque=0x555556f35610, addr=26, size=4)
at hw/display/ati.c:299
#7 0x0000555555b3a988 in ati_mm_read (opaque=0x555556f35610, addr=4, size=4)
at hw/display/ati.c:290
It's trying to do an indexed read via MM_DATA reg of the middle of reg
0x18 BIOS_2_SCRATCH which ends up calling ati_reg_read_offs with out of
bound values. Maybe we should clamp size somewhere.
Regards,
BALATON Zoltan
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https://bugs.launchpad.net/bugs/1878134
Title:
Assertion failures in ati_reg_read_offs/ati_reg_write_offs
Status in QEMU:
New
Bug description:
Hello,
While fuzzing, I found inputs that trigger assertion failures in
ati_reg_read_offs/ati_reg_write_offs
uint32_t extract32(uint32_t, int, int): Assertion `start >= 0 &&
length > 0 && length <= 32 - start' failed
#3 0x00007ffff6866092 in __GI___assert_fail (assertion=0x555556e760c0 <str>
"start >= 0 && length > 0 && length <= 32 - start", file=0x555556e76120 <str>
"/home/alxndr/Development/qemu/include/qemu/bitops.h", line=0x12c,
function=0x555556e76180 <__PRETTY_FUNCTION__.extract32> "uint32_t
extract32(uint32_t, int, int)") at assert.c:101
#4 0x000055555653d8a7 in ati_mm_read (opaque=<optimized out>, addr=0x1a,
size=<optimized out>) at
/home/alxndr/Development/qemu/include/qemu/log-for-trace.h:29
#5 0x000055555653c825 in ati_mm_read (opaque=<optimized out>, addr=0x4,
size=<optimized out>) at /home/alxndr/Development/qemu/hw/display/ati.c:289
#6 0x000055555601446e in memory_region_read_accessor (mr=0x63100004dc20,
addr=<optimized out>, value=<optimized out>, size=<optimized out>,
shift=<optimized out>, mask=<optimized out>, attrs=...) at
/home/alxndr/Development/qemu/memory.c:434
#7 0x0000555556001a70 in access_with_adjusted_size (addr=<optimized out>,
value=<optimized out>, size=<optimized out>, access_size_min=<optimized out>,
access_size_max=<optimized out>, access_fn=<optimized out>, mr=0x63100004dc20,
attrs=...) at /home/alxndr/Development/qemu/memory.c:544
#8 0x0000555556001a70 in memory_region_dispatch_read1 (mr=0x63100004dc20,
addr=0x4, pval=<optimized out>, size=0x4, attrs=...) at
/home/alxndr/Development/qemu/memory.c:1396
I can reproduce it in qemu 5.0 built with using:
cat << EOF | ~/Development/qemu/build/i386-softmmu/qemu-system-i386 -M
pc-q35-5.0 -device ati-vga -nographic -qtest stdio -monitor none -serial none
outl 0xcf8 0x80001018
outl 0xcfc 0xe2000000
outl 0xcf8 0x8000101c
outl 0xcf8 0x80001004
outw 0xcfc 0x7
outl 0xcf8 0x8000fa20
write 0xe2000004 0x1 0x1a
readq 0xe2000000
EOF
Similarly for ati_reg_write_offs:
cat << EOF | ~/Development/qemu/build/i386-softmmu/qemu-system-i386 -M
pc-q35-5.0 -device ati-vga -nographic -qtest stdio -monitor none -serial none
outl 0xcf8 0x80001018
outl 0xcfc 0xe2000000
outl 0xcf8 0x8000101c
outl 0xcf8 0x80001004
outw 0xcfc 0x7
outl 0xcf8 0x8000fa20
write 0xe2000000 0x8 0x6a00000000006a00
EOF
I also attached the traces to this launchpad report, in case the
formatting is broken:
qemu-system-i386 -M pc-q35-5.0 -device ati-vga -nographic -qtest stdio
-monitor none -serial none < attachment
Please let me know if I can provide any further info.
-Alex
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- Re: [Bug 1878134] [NEW] Assertion failures in ati_reg_read_offs/ati_reg_write_offs,
BALATON Zoltan <=