Re: [Qemu-devel] [PATCH 3/3] hw/machine: Free old values of string properties

Re: [Qemu-devel] [PATCH 3/3] hw/machine: Free old values of string properties

[Marcel Apfelbaum]

On Fri, 2014-05-30 at 17:02 -0300, Eduardo Habkost wrote:
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Cc: Marcel Apfelbaum <marcel.a@redhat.com>
> Cc: Andreas Färber <afaerber@suse.de>
> ---
>  hw/core/machine.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index cbba679..df612bb 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -24,6 +24,7 @@ static void machine_set_accel(Object *obj, const char *value, Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
>  
> +    g_free(ms->accel);
I am not sure if in QMP is not caller's responsibility to free the input string.
If I think about it, I ask an object to set "my" string and it deletes it :(...
Same for the others.

Added Markus and Luiz, maybe they have an opinion on that.
Thanks,
Marcel
 
>      ms->accel = g_strdup(value);
>  }
>  
> @@ -79,6 +80,7 @@ static void machine_set_kernel(Object *obj, const char *value, Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
>  
> +    g_free(ms->kernel_filename);
>      ms->kernel_filename = g_strdup(value);
>  }
>  
> @@ -93,6 +95,7 @@ static void machine_set_initrd(Object *obj, const char *value, Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
>  
> +    g_free(ms->initrd_filename);
>      ms->initrd_filename = g_strdup(value);
>  }
>  
> @@ -107,6 +110,7 @@ static void machine_set_append(Object *obj, const char *value, Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
>  
> +    g_free(ms->kernel_cmdline);
>      ms->kernel_cmdline = g_strdup(value);
>  }
>  
> @@ -121,6 +125,7 @@ static void machine_set_dtb(Object *obj, const char *value, Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
>  
> +    g_free(ms->dtb);
>      ms->dtb = g_strdup(value);
>  }
>  
> @@ -135,6 +140,7 @@ static void machine_set_dumpdtb(Object *obj, const char *value, Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
>  
> +    g_free(ms->dumpdtb);
>      ms->dumpdtb = g_strdup(value);
>  }
>  
> @@ -176,6 +182,7 @@ static void machine_set_dt_compatible(Object *obj, const char *value, Error **er
>  {
>      MachineState *ms = MACHINE(obj);
>  
> +    g_free(ms->dt_compatible);
>      ms->dt_compatible = g_strdup(value);
>  }
>  
> @@ -232,6 +239,7 @@ static void machine_set_firmware(Object *obj, const char *value, Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
>  
> +    g_free(ms->firmware);
>      ms->firmware = g_strdup(value);
>  }
>  

Re: [Qemu-devel] [PATCH 3/3] hw/machine: Free old values of string properties

[Markus Armbruster]

Marcel Apfelbaum <marcel.a@redhat.com> writes:

> On Fri, 2014-05-30 at 17:02 -0300, Eduardo Habkost wrote:
>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>> ---
>> Cc: Marcel Apfelbaum <marcel.a@redhat.com>
>> Cc: Andreas Färber <afaerber@suse.de>
>> ---
>>  hw/core/machine.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>> 
>> diff --git a/hw/core/machine.c b/hw/core/machine.c
>> index cbba679..df612bb 100644
>> --- a/hw/core/machine.c
>> +++ b/hw/core/machine.c
>> @@ -24,6 +24,7 @@ static void machine_set_accel(Object *obj, const char *value, Error **errp)
>>  {
>>      MachineState *ms = MACHINE(obj);
>>  
>> +    g_free(ms->accel);
> I am not sure if in QMP is not caller's responsibility to free the input string.
> If I think about it, I ask an object to set "my" string and it deletes it :(...
> Same for the others.
>
> Added Markus and Luiz, maybe they have an opinion on that.
>
>>      ms->accel = g_strdup(value);
>>  }
>>  

Misunderstanding?  Eduardo's patch frees the old value before it
overwrites it.  It doesn't free "the input string", assuming by "the
input string" you mean argument value.

Re: [Qemu-devel] [PATCH 3/3] hw/machine: Free old values of string properties

[Marcel Apfelbaum]

On Mon, 2014-06-02 at 13:51 +0200, Markus Armbruster wrote:
> Marcel Apfelbaum <marcel.a@redhat.com> writes:
> 
> > On Fri, 2014-05-30 at 17:02 -0300, Eduardo Habkost wrote:
> >> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> >> ---
> >> Cc: Marcel Apfelbaum <marcel.a@redhat.com>
> >> Cc: Andreas Färber <afaerber@suse.de>
> >> ---
> >>  hw/core/machine.c | 8 ++++++++
> >>  1 file changed, 8 insertions(+)
> >> 
> >> diff --git a/hw/core/machine.c b/hw/core/machine.c
> >> index cbba679..df612bb 100644
> >> --- a/hw/core/machine.c
> >> +++ b/hw/core/machine.c
> >> @@ -24,6 +24,7 @@ static void machine_set_accel(Object *obj, const char *value, Error **errp)
> >>  {
> >>      MachineState *ms = MACHINE(obj);
> >>  
> >> +    g_free(ms->accel);
> > I am not sure if in QMP is not caller's responsibility to free the input string.
> > If I think about it, I ask an object to set "my" string and it deletes it :(...
> > Same for the others.
> >
> > Added Markus and Luiz, maybe they have an opinion on that.
> >
> >>      ms->accel = g_strdup(value);
> >>  }
> >>  
> 
> Misunderstanding?  Eduardo's patch frees the old value before it
> overwrites it.  It doesn't free "the input string", assuming by "the
> input string" you mean argument value.

You are right! My bad, for some reason I saw g_free(value), but it
was me not reading it right :(.

Thanks,
Marcel

Re: [Qemu-devel] [PATCH 3/3] hw/machine: Free old values of string properties

[Markus Armbruster]

Marcel Apfelbaum <marcel.a@redhat.com> writes:

> On Mon, 2014-06-02 at 13:51 +0200, Markus Armbruster wrote:
>> Marcel Apfelbaum <marcel.a@redhat.com> writes:
>> 
>> > On Fri, 2014-05-30 at 17:02 -0300, Eduardo Habkost wrote:
>> >> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>> >> ---
>> >> Cc: Marcel Apfelbaum <marcel.a@redhat.com>
>> >> Cc: Andreas Färber <afaerber@suse.de>
>> >> ---
>> >>  hw/core/machine.c | 8 ++++++++
>> >>  1 file changed, 8 insertions(+)
>> >> 
>> >> diff --git a/hw/core/machine.c b/hw/core/machine.c
>> >> index cbba679..df612bb 100644
>> >> --- a/hw/core/machine.c
>> >> +++ b/hw/core/machine.c
>> >> @@ -24,6 +24,7 @@ static void machine_set_accel(Object *obj, const char *value, Error **errp)
>> >>  {
>> >>      MachineState *ms = MACHINE(obj);
>> >>  
>> >> +    g_free(ms->accel);
>> > I am not sure if in QMP is not caller's responsibility to free the
>> > input string.
>> > If I think about it, I ask an object to set "my" string and it
>> > deletes it :(...
>> > Same for the others.
>> >
>> > Added Markus and Luiz, maybe they have an opinion on that.
>> >
>> >>      ms->accel = g_strdup(value);
>> >>  }
>> >>  
>> 
>> Misunderstanding?  Eduardo's patch frees the old value before it
>> overwrites it.  It doesn't free "the input string", assuming by "the
>> input string" you mean argument value.
>
> You are right! My bad, for some reason I saw g_free(value), but it
> was me not reading it right :(.

Happens :)

Reviewed-by: Markus Armbruster <armbru@redhat.com>

Re: [Qemu-devel] [PATCH 3/3] hw/machine: Free old values of string properties

[Marcel Apfelbaum]

On Mon, 2014-06-02 at 14:52 +0200, Markus Armbruster wrote:
> Marcel Apfelbaum <marcel.a@redhat.com> writes:
> 
> > On Mon, 2014-06-02 at 13:51 +0200, Markus Armbruster wrote:
> >> Marcel Apfelbaum <marcel.a@redhat.com> writes:
> >> 
> >> > On Fri, 2014-05-30 at 17:02 -0300, Eduardo Habkost wrote:
> >> >> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> >> >> ---
> >> >> Cc: Marcel Apfelbaum <marcel.a@redhat.com>
> >> >> Cc: Andreas Färber <afaerber@suse.de>
> >> >> ---
> >> >>  hw/core/machine.c | 8 ++++++++
> >> >>  1 file changed, 8 insertions(+)
> >> >> 
> >> >> diff --git a/hw/core/machine.c b/hw/core/machine.c
> >> >> index cbba679..df612bb 100644
> >> >> --- a/hw/core/machine.c
> >> >> +++ b/hw/core/machine.c
> >> >> @@ -24,6 +24,7 @@ static void machine_set_accel(Object *obj, const char *value, Error **errp)
> >> >>  {
> >> >>      MachineState *ms = MACHINE(obj);
> >> >>  
> >> >> +    g_free(ms->accel);
> >> > I am not sure if in QMP is not caller's responsibility to free the
> >> > input string.
> >> > If I think about it, I ask an object to set "my" string and it
> >> > deletes it :(...
> >> > Same for the others.
> >> >
> >> > Added Markus and Luiz, maybe they have an opinion on that.
> >> >
> >> >>      ms->accel = g_strdup(value);
> >> >>  }
> >> >>  
> >> 
> >> Misunderstanding?  Eduardo's patch frees the old value before it
> >> overwrites it.  It doesn't free "the input string", assuming by "the
> >> input string" you mean argument value.
> >
> > You are right! My bad, for some reason I saw g_free(value), but it
> > was me not reading it right :(.
> 
> Happens :)
> 
> Reviewed-by: Markus Armbruster <armbru@redhat.com>

Yes indeed.
Reviewed-by: Marcel Apfelbaum <marcel.a@redhat.com>

Re: [Qemu-devel] [PATCH 1/3] rng-random: NULL check not needed before g_free()

[Markus Armbruster]

Eduardo Habkost <ehabkost@redhat.com> writes:

> g_free() is NULL-safe.
>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Cc: Anthony Liguori <aliguori@amazon.com>
> Cc: Luiz Capitulino <lcapitulino@redhat.com>
> ---
>  backends/rng-random.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/backends/rng-random.c b/backends/rng-random.c
> index 136499d..601d9dc 100644
> --- a/backends/rng-random.c
> +++ b/backends/rng-random.c
> @@ -106,10 +106,7 @@ static void rng_random_set_filename(Object *obj, const char *filename,
>          return;
>      }
>  
> -    if (s->filename) {
> -        g_free(s->filename);
> -    }
> -
> +    g_free(s->filename);
>      s->filename = g_strdup(filename);
>  }

Reviewed-by: Markus Armbruster <armbru@redhat.com>


Note there are a quite a few more instances of this anti-pattern.
Coccinelle can find them, semantic patch appended.  Beware, it can throw
away comments in the conditional, which is usually not what we want.


@@
expression E;
@@
-	if (E != NULL) {
-	    g_free(E);
-	}
+       g_free(E);

Re: [Qemu-devel] [PATCH 1/3] rng-random: NULL check not needed before g_free()

[Amos Kong]

On Mon, Jun 02, 2014 at 01:38:52PM +0200, Markus Armbruster wrote:
> Eduardo Habkost <ehabkost@redhat.com> writes:
> 
> > g_free() is NULL-safe.
> >
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> > Cc: Anthony Liguori <aliguori@amazon.com>
> > Cc: Luiz Capitulino <lcapitulino@redhat.com>
> > ---
> >  backends/rng-random.c | 5 +----
> >  1 file changed, 1 insertion(+), 4 deletions(-)
> >
> > diff --git a/backends/rng-random.c b/backends/rng-random.c
> > index 136499d..601d9dc 100644
> > --- a/backends/rng-random.c
> > +++ b/backends/rng-random.c
> > @@ -106,10 +106,7 @@ static void rng_random_set_filename(Object *obj, const char *filename,
> >          return;
> >      }
> >  
> > -    if (s->filename) {
> > -        g_free(s->filename);
> > -    }
> > -
> > +    g_free(s->filename);
> >      s->filename = g_strdup(filename);
> >  }
> 
> Reviewed-by: Markus Armbruster <armbru@redhat.com>
> 
> 
> Note there are a quite a few more instances of this anti-pattern.
> Coccinelle can find them, semantic patch appended.  Beware, it can throw
> away comments in the conditional, which is usually not what we want.
> 
> 
> @@
> expression E;
> @@
> -	if (E != NULL) {
> -	    g_free(E);
> -	}
> +       g_free(E);

[amos@z qemu]$ grep g_free -B 2 -r * |less

then try to search "/if.*NULL"

Not all can be found by this way, but many instances are found.

-- 
			Amos.

Re: [Qemu-devel] [PATCH 1/3] rng-random: NULL check not needed before g_free()

[Luiz Capitulino]

On Fri, 30 May 2014 17:02:18 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> g_free() is NULL-safe.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

This one should to go through qemu-trivial (CCed).

> ---
> Cc: Anthony Liguori <aliguori@amazon.com>
> Cc: Luiz Capitulino <lcapitulino@redhat.com>
> ---
>  backends/rng-random.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/backends/rng-random.c b/backends/rng-random.c
> index 136499d..601d9dc 100644
> --- a/backends/rng-random.c
> +++ b/backends/rng-random.c
> @@ -106,10 +106,7 @@ static void rng_random_set_filename(Object *obj, const char *filename,
>          return;
>      }
>  
> -    if (s->filename) {
> -        g_free(s->filename);
> -    }
> -
> +    g_free(s->filename);
>      s->filename = g_strdup(filename);
>  }
>  

Re: [Qemu-devel] [Qemu-trivial] [PATCH 1/3] rng-random: NULL check not needed before g_free()

[Michael Tokarev]

10.06.2014 00:04, Luiz Capitulino wrote:
> On Fri, 30 May 2014 17:02:18 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
>> g_free() is NULL-safe.

Applied to -trivial, thank you!

/mjt

Re: [Qemu-devel] [PATCH 2/3] rng-egd: Free old chr_name value before setting new one

[Markus Armbruster]

Eduardo Habkost <ehabkost@redhat.com> writes:

> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Cc: Anthony Liguori <aliguori@amazon.com>
> Cc: Amos Kong <akong@redhat.com>
> ---
>  backends/rng-egd.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/backends/rng-egd.c b/backends/rng-egd.c
> index 25bb3b4..2962795 100644
> --- a/backends/rng-egd.c
> +++ b/backends/rng-egd.c
> @@ -169,6 +169,7 @@ static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
>      if (b->opened) {
>          error_set(errp, QERR_PERMISSION_DENIED);
>      } else {
> +        g_free(s->chr_name);
>          s->chr_name = g_strdup(value);
>      }
>  }

I see you searched for the bug elsewhere.  Appreciated.  Do you think
you got them all?

Aside: I hate

    if (bad) {
        handle error
    } else {
        continue normal work
    }

The normal flow gets nested deeper and deeper.  When the code grows,
normal work can easily end up after the conditional by mistake.  Better:

    if (bad) {
        handle error
        return
    }
    continue normal work

Anyway, not your fault.

Reviewed-by: Markus Armbruster <armbru@redhat.com>

Re: [Qemu-devel] [PATCH 2/3] rng-egd: Free old chr_name value before setting new one

[Eduardo Habkost]

On Mon, Jun 02, 2014 at 02:58:05PM +0200, Markus Armbruster wrote:
> Eduardo Habkost <ehabkost@redhat.com> writes:
> 
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> > Cc: Anthony Liguori <aliguori@amazon.com>
> > Cc: Amos Kong <akong@redhat.com>
> > ---
> >  backends/rng-egd.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/backends/rng-egd.c b/backends/rng-egd.c
> > index 25bb3b4..2962795 100644
> > --- a/backends/rng-egd.c
> > +++ b/backends/rng-egd.c
> > @@ -169,6 +169,7 @@ static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
> >      if (b->opened) {
> >          error_set(errp, QERR_PERMISSION_DENIED);
> >      } else {
> > +        g_free(s->chr_name);
> >          s->chr_name = g_strdup(value);
> >      }
> >  }
> 
> I see you searched for the bug elsewhere.  Appreciated.  Do you think
> you got them all?

I grepped for all object_property_add_str occurrences, and (unless I
made a mistake) I fixed all of them.

-- 
Eduardo