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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 9 Apr 2015 15:48:57 +0100
Message-ID: <CAFEAcA_xNXPbkeJth8_2=h9JPObD4i0MBZbkp=V-9eVoxq7kcA@mail.gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] Fix crash with illegal "-net nic,
	model=xxx" option
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Thomas Huth <thuth@redhat.com>, Jason Wang <jasowang@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>

On 9 April 2015 at 14:37, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Thu, Apr 09, 2015 at 03:32:45PM +0200, Thomas Huth wrote:
>> Current QEMU crashes when specifying an illegal model with the
>> "-net nic,model=xxx" option, e.g.:
>>
>>  $ qemu-system-x86_64 -net nic,model=n/a
>>  qemu-system-x86_64: Unsupported NIC model: n/a
>>
>>  Program received signal SIGSEGV, Segmentation fault.
>>
>> The gdb backtrace looks like this:
>>
>> 0x0000555555965fe0 in error_get_pretty (err=0x0) at util/error.c:152
>> 152       return err->msg;
>> (gdb) bt
>>  0  0x0000555555965fe0 in error_get_pretty (err=0x0) at util/error.c:152
>>  1  0x0000555555965ffd in error_report_err (err=0x0) at util/error.c:157
>>  2  0x0000555555809c90 in pci_nic_init_nofail (nd=0x555555e49860 <nd_table>, rootbus=0x5555564409b0,
>>     default_model=0x55555598c37b "e1000", default_devaddr=0x0) at hw/pci/pci.c:1663
>>  3  0x0000555555691e42 in pc_nic_init (isa_bus=0x555556f71900, pci_bus=0x5555564409b0)
>>     at hw/i386/pc.c:1506
>>  4  0x000055555569396b in pc_init1 (machine=0x5555562abbf0, pci_enabled=1, kvmclock_enabled=1)
>>     at hw/i386/pc_piix.c:248
>>  5  0x0000555555693d27 in pc_init_pci (machine=0x5555562abbf0) at hw/i386/pc_piix.c:310
>>  6  0x000055555572ddf5 in main (argc=3, argv=0x7fffffffe018, envp=0x7fffffffe038) at vl.c:4226
>>
>> The problem is that pci_nic_init_nofail() does not check whether the err
>> parameter from pci_nic_init has been set up and thus passes a NULL pointer
>> to error_report_err(). Fix it by correctly checking the err parameter.
>>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>
> Thanks!
> Given that this is a legacy -net option, I'm inclined
> to fix it post-2.3, and Cc stable.
> Unfortunately I won't be able to do a pull request before rc3.

Since this is a pretty safe and simple change I'm happy to apply
it direct to master if you like. Do you want to provide a reviewed-by
tag?

thanks
-- PMM