Re: Uninitialized variables in hvm_event_breakpoint (Re: New Defects reported by Coverity Scan for XenProject)

[Razvan Cojocaru <rcojocaru@bitdefender.com>]

On 02/18/2016 12:01 PM, Ian Campbell wrote:
> On Wed, 2016-02-17 at 16:02 -0800, scan-admin@coverity.com wrote:
>> Hi,
>>
>> Please find the latest report on new defect(s) introduced to XenProject
>> found with Coverity Scan.
>>
>> 1 new defect(s) introduced to XenProject found with Coverity Scan.
>> 4 defect(s), reported by Coverity Scan earlier, were marked fixed in the
>> recent build analyzed by Coverity Scan.
>>
>> New defect(s) Reported-by: Coverity Scan
>> Showing 1 of 1 defect(s)
>>
>>
>> ** CID 1353192:  Uninitialized variables  (UNINIT)
>> /xen/arch/x86/hvm/event.c: 176 in hvm_event_breakpoint()
> 
> This appears to have been introduced by: 
>     commit
>     557c7873f35aa39bd84977b28948457b1b342f92
>     Author: Corneliu ZUZU <czuzu@bitdef
>     ender.com>
>     Date:   Mon Feb 15 14:14:16 2016 +0100
> 
>         x86: merge 2 hvm_event_... functions into 1
>         
>         This patch merges almost identical functions hvm_event_int3 and
>         hvm_event_single_step into a single function called hvm_event_breakpoint.
>         Also fixes event.c file header comment in the process.
>         
>         Signed-off-by: Corneliu ZUZU <    czuzu@bitdefender.com    >
>         Acked-by: Razvan Cojocaru <    rcojocaru@bitdefender.com    >
>         Acked-by: Jan Beulich <    jbeulich@suse.com    >
> 
> 
> hvm_event_breakpoint calls hvm_event_traps(&req) and if sync is true that
> ors some bits into req->flags which was never initialised.
> 
>>
>>
>> _________________________________________________________________________
>> _______________________________
>> *** CID 1353192:  Uninitialized variables  (UNINIT)
>> /xen/arch/x86/hvm/event.c: 176 in hvm_event_breakpoint()
>> 170     
>> 171     int hvm_event_breakpoint(unsigned long rip,
>> 172                              enum hvm_event_breakpoint_type type)
>> 173     {
>> 174         struct vcpu *curr = current;
>> 175         struct arch_domain *ad = &curr->domain->arch;
>>>>>     CID 1353192:  Uninitialized variables  (UNINIT)
>>>>>     Declaring variable "req" without initializer.
>> 176         vm_event_request_t req;
>> 177     
>> 178         switch ( type )
>> 179         {
>> 180         case HVM_EVENT_SOFTWARE_BREAKPOINT:
>> 181             if ( !ad->monitor.software_breakpoint_enabled )

But the structure is being initialized in both cases
(HVM_EVENT_SOFTWARE_BREAKPOINT and HVM_EVENT_SINGLESTEP_BREAKPOINT), and
the default case returns, so it's not possible to get to the
hvm_event_traps(&req) call with an uninitialized req. Am I missing
something?


Thanks,
Razvan