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[Qemu-devel] [Bug 1527322] Re: undefined behavior issues
From: |
Octoploid |
Subject: |
[Qemu-devel] [Bug 1527322] Re: undefined behavior issues |
Date: |
Thu, 17 Dec 2015 17:00:23 -0000 |
Program received signal SIGSEGV, Segmentation fault.
thread_pool_submit_aio (pool=0x0, func=0x555555820bc0 <coroutine_enter_func>,
arg=0x5555579db430, cb=<optimized out>, opaque=<optimized out>)
at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/thread-pool.c:246
246 QLIST_INSERT_HEAD(&pool->head, req, all);
(gdb) bt
#0 thread_pool_submit_aio (pool=0x0, func=0x555555820bc0
<coroutine_enter_func>, arg=0x5555579db430, cb=<optimized out>,
opaque=<optimized out>)
at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/thread-pool.c:246
#1 0x00005555559451cd in aio_bh_call (bh=<optimized out>) at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/async.c:64
#2 aio_bh_poll (address@hidden) at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/async.c:92
#3 0x00005555559524f0 in aio_dispatch (ctx=0x5555561c1da0) at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/aio-posix.c:305
#4 0x0000555555944f4e in aio_ctx_dispatch (source=<optimized out>,
callback=<optimized out>, user_data=<optimized out>)
at /var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/async.c:231
#5 0x00007ffff726ce2e in g_main_context_dispatch () from
/usr/lib/libglib-2.0.so.0
#6 0x0000555555950baa in glib_pollfds_poll () at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/main-loop.c:211
#7 os_host_main_loop_wait (timeout=<optimized out>) at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/main-loop.c:256
#8 main_loop_wait (nonblocking=<optimized out>) at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/main-loop.c:504
#9 0x00005555556ddf46 in main_loop () at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/vl.c:1923
#10 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/vl.c:4684
(gdb) p pool
$1 = (ThreadPool *) 0x0
--
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https://bugs.launchpad.net/bugs/1527322
Title:
undefined behavior issues
Status in QEMU:
New
Bug description:
Building qemu-2.5.0 with -fsanitize=undefined shows, e.g.:
address@hidden linux % qemu-system-x86_64 -s -enable-kvm -net
nic,vlan=0,model=virtio -net user -fsdev
local,security_model=none,id=root,path=/ -device virtio-9p-pci,id=root,fsdev
=root,mount_tag=/dev/root -m 512 -smp 2 -kernel
/usr/src/linux/arch/x86/boot/bzImage -nographic -append "init=/bin/zsh
root=/dev/root console=ttyS0 kgdboc=ttyS0 rootflags=rw,
trans=virtio rootfstype=9p ip=dhcp earlyprintk=ttyS0"
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/exec.c:307:5:
runtime error: variable length array bound evaluates to non-positive value 0
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/hw/i386/kvm/apic.c:37:47:
runtime error: left shift of 15 by 28 places cannot be represented in type
'int'
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/include/qemu/rcu.h:85:21:
runtime error: member access within null pointer of type 'struct
rcu_reader_data'
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/include/qemu/rcu.h:101:5:
runtime error: member access within null pointer of type 'struct
rcu_reader_data'
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/include/qemu/rcu.h:102:8:
runtime error: member access within null pointer of type 'struct
rcu_reader_data'
...
ALSA device list:
No soundcards found.
/var/tmp/portage/app-emulation/qemu-2.5.0/work/qemu-2.5.0/thread-pool.c:246:5:
runtime error: member access within null pointer of type 'struct ThreadPool'
[1] 9295 segmentation fault qemu-system-x86_64 -s -enable-kvm -net
nic,vlan=0,model=virtio -net user
As you can see it segfaults when build with upcoming gcc-6, that is more
aggressive when it comes to undefined behavior.
The compiler just assumes that "this" can never be NULL and optimizes
accordingly.
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