[PATCH] vl: Fix an assert failure in error path

[PATCH] vl: Fix an assert failure in error path

[Zhenzhong Duan]

Based on the description of error_setg(), the local variable err in
qemu_maybe_daemonize() should be initialized to NULL.

Without fix, the uninitialized *errp triggers assert failure which
doesn't show much valuable information.

Before the fix:
qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion `*errp == NULL' failed.

After fix:
qemu-system-x86_64: cannot create PID file: Cannot open pid file: Permission denied

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
 softmmu/vl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/softmmu/vl.c b/softmmu/vl.c
index 326c1e9080..feb4d201f3 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2522,7 +2522,7 @@ static void qemu_process_help_options(void)
 
 static void qemu_maybe_daemonize(const char *pid_file)
 {
-    Error *err;
+    Error *err = NULL;
 
     os_daemonize();
     rcu_disable_atfork();
-- 
2.25.1

Re: [PATCH] vl: Fix an assert failure in error path

[Paolo Bonzini]

On 10/06/21 10:47, Zhenzhong Duan wrote:
> Based on the description of error_setg(), the local variable err in
> qemu_maybe_daemonize() should be initialized to NULL.
> 
> Without fix, the uninitialized *errp triggers assert failure which
> doesn't show much valuable information.
> 
> Before the fix:
> qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion `*errp == NULL' failed.
> 
> After fix:
> qemu-system-x86_64: cannot create PID file: Cannot open pid file: Permission denied
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>   softmmu/vl.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index 326c1e9080..feb4d201f3 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -2522,7 +2522,7 @@ static void qemu_process_help_options(void)
>   
>   static void qemu_maybe_daemonize(const char *pid_file)
>   {
> -    Error *err;
> +    Error *err = NULL;
>   
>       os_daemonize();
>       rcu_disable_atfork();
> 

Queued, thanks.

Paolo

Re: [PATCH] vl: Fix an assert failure in error path

[Markus Armbruster]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 10/06/21 10:47, Zhenzhong Duan wrote:
>> Based on the description of error_setg(), the local variable err in
>> qemu_maybe_daemonize() should be initialized to NULL.
>> Without fix, the uninitialized *errp triggers assert failure which
>> doesn't show much valuable information.
>> Before the fix:
>> qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion `*errp == NULL' failed.
>> After fix:
>> qemu-system-x86_64: cannot create PID file: Cannot open pid file: Permission denied
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> ---
>>   softmmu/vl.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>> diff --git a/softmmu/vl.c b/softmmu/vl.c
>> index 326c1e9080..feb4d201f3 100644
>> --- a/softmmu/vl.c
>> +++ b/softmmu/vl.c
>> @@ -2522,7 +2522,7 @@ static void qemu_process_help_options(void)
>>     static void qemu_maybe_daemonize(const char *pid_file)
>>   {
>> -    Error *err;
>> +    Error *err = NULL;

Common mistake, I'm afraid.

>>         os_daemonize();
>>       rcu_disable_atfork();
>> 
>
> Queued, thanks.

Suggest to amend the commit message with

    Fixes: 03d2b412aaf2078425f8472f31c8a9c2340969eb

Re: [PATCH] vl: Fix an assert failure in error path

[Daniel P. Berrangé]

On Wed, Jun 09, 2021 at 02:09:47PM +0200, Markus Armbruster wrote:
> Paolo Bonzini <pbonzini@redhat.com> writes:
> 
> > On 10/06/21 10:47, Zhenzhong Duan wrote:
> >> Based on the description of error_setg(), the local variable err in
> >> qemu_maybe_daemonize() should be initialized to NULL.
> >> Without fix, the uninitialized *errp triggers assert failure which
> >> doesn't show much valuable information.
> >> Before the fix:
> >> qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion `*errp == NULL' failed.
> >> After fix:
> >> qemu-system-x86_64: cannot create PID file: Cannot open pid file: Permission denied
> >> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> >> ---
> >>   softmmu/vl.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >> diff --git a/softmmu/vl.c b/softmmu/vl.c
> >> index 326c1e9080..feb4d201f3 100644
> >> --- a/softmmu/vl.c
> >> +++ b/softmmu/vl.c
> >> @@ -2522,7 +2522,7 @@ static void qemu_process_help_options(void)
> >>     static void qemu_maybe_daemonize(const char *pid_file)
> >>   {
> >> -    Error *err;
> >> +    Error *err = NULL;
> 
> Common mistake, I'm afraid.

Initializing isn't likely to be a performance impact, so I'd think
we should make 'checkpatch.pl' complain about any 'Error *' variable
that is not initialized to NULL, as a safety net, even if not technically
required in some cases.

Regards,
Daniel
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Re: [PATCH] vl: Fix an assert failure in error path

[Peng Liang]

On 6/9/2021 8:15 PM, Daniel P. Berrangé wrote:
> On Wed, Jun 09, 2021 at 02:09:47PM +0200, Markus Armbruster wrote:
>> Paolo Bonzini <pbonzini@redhat.com> writes:
>>
>>> On 10/06/21 10:47, Zhenzhong Duan wrote:
>>>> Based on the description of error_setg(), the local variable err in
>>>> qemu_maybe_daemonize() should be initialized to NULL.
>>>> Without fix, the uninitialized *errp triggers assert failure which
>>>> doesn't show much valuable information.
>>>> Before the fix:
>>>> qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion `*errp == NULL' failed.
>>>> After fix:
>>>> qemu-system-x86_64: cannot create PID file: Cannot open pid file: Permission denied
>>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>>> ---
>>>>   softmmu/vl.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>> diff --git a/softmmu/vl.c b/softmmu/vl.c
>>>> index 326c1e9080..feb4d201f3 100644
>>>> --- a/softmmu/vl.c
>>>> +++ b/softmmu/vl.c
>>>> @@ -2522,7 +2522,7 @@ static void qemu_process_help_options(void)
>>>>     static void qemu_maybe_daemonize(const char *pid_file)
>>>>   {
>>>> -    Error *err;
>>>> +    Error *err = NULL;
>>
>> Common mistake, I'm afraid.
> 
> Initializing isn't likely to be a performance impact, so I'd think
> we should make 'checkpatch.pl' complain about any 'Error *' variable
> that is not initialized to NULL, as a safety net, even if not technically
> required in some cases.
> 
> Regards,
> Daniel
> 

Hi,
Could we add a coccinelle script to check (and fix) these problems?  e.g.:
@ r @
identifier id;
@@
  Error *id
+ = NULL
  ;

Using this script, I found that local variable err in
qemu_init_subsystems is not initialized to NULL too.  The script is not
prefect though, it will initialize all global/static 'Error *' variables
and all local 'Error *' variables in util/error.c to NULL, which is
unnecessary.

Thanks,
Peng

Re: [PATCH] vl: Fix an assert failure in error path

[Markus Armbruster]

Peng Liang <liangpeng10@huawei.com> writes:

> On 6/9/2021 8:15 PM, Daniel P. Berrangé wrote:
>> On Wed, Jun 09, 2021 at 02:09:47PM +0200, Markus Armbruster wrote:
>>> Paolo Bonzini <pbonzini@redhat.com> writes:
>>>
>>>> On 10/06/21 10:47, Zhenzhong Duan wrote:
>>>>> Based on the description of error_setg(), the local variable err in
>>>>> qemu_maybe_daemonize() should be initialized to NULL.
>>>>> Without fix, the uninitialized *errp triggers assert failure which
>>>>> doesn't show much valuable information.
>>>>> Before the fix:
>>>>> qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion `*errp == NULL' failed.
>>>>> After fix:
>>>>> qemu-system-x86_64: cannot create PID file: Cannot open pid file: Permission denied
>>>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>>>> ---
>>>>>   softmmu/vl.c | 2 +-
>>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>> diff --git a/softmmu/vl.c b/softmmu/vl.c
>>>>> index 326c1e9080..feb4d201f3 100644
>>>>> --- a/softmmu/vl.c
>>>>> +++ b/softmmu/vl.c
>>>>> @@ -2522,7 +2522,7 @@ static void qemu_process_help_options(void)
>>>>>     static void qemu_maybe_daemonize(const char *pid_file)
>>>>>   {
>>>>> -    Error *err;
>>>>> +    Error *err = NULL;
>>>
>>> Common mistake, I'm afraid.
>> 
>> Initializing isn't likely to be a performance impact, so I'd think
>> we should make 'checkpatch.pl' complain about any 'Error *' variable
>> that is not initialized to NULL, as a safety net, even if not technically
>> required in some cases.
>> 
>> Regards,
>> Daniel
>> 
>
> Hi,
> Could we add a coccinelle script to check (and fix) these problems?  e.g.:

Coccinelle is good for finding and fixing instances of bad patterns that
have crept in.  checkpatch is good for keeping them out.  Both has its
uses.

> @ r @
> identifier id;
> @@
>   Error *id
> + = NULL
>   ;
>
> Using this script, I found that local variable err in
> qemu_init_subsystems is not initialized to NULL too.

Crash bug, broken in commit efd7ab22fb "vl: extract
qemu_init_subsystems", v6.0.0.  Care to submit a fix?

>                                                       The script is not
> prefect though, it will initialize all global/static 'Error *' variables
> and all local 'Error *' variables in util/error.c to NULL, which is
> unnecessary.

Excluding util/error.c is easy once you know how to:

    @ depends on !(file in "util/error.c")@
    identifier id;
    @@
    ...

Excluding variable definitions with static storage duraction shouldn't
be too hard, either.  If Coccinelle is sufficiently clever, adding
keyword auto suffices.  Else, try matching keyword static separately,
like so:

    (
        static Error *id;
    |
    -   Error *id;
    +   Error *id = NULL;
    )

Completely untested.

Re: [PATCH] vl: Fix an assert failure in error path

[Peng Liang]

On 6/10/2021 3:32 PM, Markus Armbruster wrote:
> Peng Liang <liangpeng10@huawei.com> writes:
> 
>> On 6/9/2021 8:15 PM, Daniel P. Berrangé wrote:
>>> On Wed, Jun 09, 2021 at 02:09:47PM +0200, Markus Armbruster wrote:
>>>> Paolo Bonzini <pbonzini@redhat.com> writes:
>>>>
>>>>> On 10/06/21 10:47, Zhenzhong Duan wrote:
>>>>>> Based on the description of error_setg(), the local variable err in
>>>>>> qemu_maybe_daemonize() should be initialized to NULL.
>>>>>> Without fix, the uninitialized *errp triggers assert failure which
>>>>>> doesn't show much valuable information.
>>>>>> Before the fix:
>>>>>> qemu-system-x86_64: ../util/error.c:59: error_setv: Assertion `*errp == NULL' failed.
>>>>>> After fix:
>>>>>> qemu-system-x86_64: cannot create PID file: Cannot open pid file: Permission denied
>>>>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>>>>> ---
>>>>>>   softmmu/vl.c | 2 +-
>>>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>> diff --git a/softmmu/vl.c b/softmmu/vl.c
>>>>>> index 326c1e9080..feb4d201f3 100644
>>>>>> --- a/softmmu/vl.c
>>>>>> +++ b/softmmu/vl.c
>>>>>> @@ -2522,7 +2522,7 @@ static void qemu_process_help_options(void)
>>>>>>     static void qemu_maybe_daemonize(const char *pid_file)
>>>>>>   {
>>>>>> -    Error *err;
>>>>>> +    Error *err = NULL;
>>>>
>>>> Common mistake, I'm afraid.
>>>
>>> Initializing isn't likely to be a performance impact, so I'd think
>>> we should make 'checkpatch.pl' complain about any 'Error *' variable
>>> that is not initialized to NULL, as a safety net, even if not technically
>>> required in some cases.
>>>
>>> Regards,
>>> Daniel
>>>
>>
>> Hi,
>> Could we add a coccinelle script to check (and fix) these problems?  e.g.:
> 
> Coccinelle is good for finding and fixing instances of bad patterns that
> have crept in.  checkpatch is good for keeping them out.  Both has its
> uses.
> 
>> @ r @
>> identifier id;
>> @@
>>   Error *id
>> + = NULL
>>   ;
>>
>> Using this script, I found that local variable err in
>> qemu_init_subsystems is not initialized to NULL too.
> 
> Crash bug, broken in commit efd7ab22fb "vl: extract
> qemu_init_subsystems", v6.0.0.  Care to submit a fix?

Have sent :)

> 
>>                                                       The script is not
>> prefect though, it will initialize all global/static 'Error *' variables
>> and all local 'Error *' variables in util/error.c to NULL, which is
>> unnecessary.
> 
> Excluding util/error.c is easy once you know how to:
> 
>     @ depends on !(file in "util/error.c")@
>     identifier id;
>     @@
>     ...
> 
> Excluding variable definitions with static storage duraction shouldn't
> be too hard, either.  If Coccinelle is sufficiently clever, adding
> keyword auto suffices.  Else, try matching keyword static separately,
> like so:
> 
>     (
>         static Error *id;
>     |
>     -   Error *id;
>     +   Error *id = NULL;
>     )
> 
> Completely untested.
> 

Thanks for your improvement!

Thanks,
Peng

Re: [PATCH] vl: Fix an assert failure in error path

[Paolo Bonzini]

On 09/06/21 14:09, Markus Armbruster wrote:
> Fixes: 03d2b412aaf2078425f8472f31c8a9c2340969eb

Actually 0546c0609c ("vl: split various early command line options to a 
separate function", 2020-12-10).

Done, thanks!

Paolo