Re: [PATCH] migration: use parameters.mode in cpr_state_save

[Fabiano Rosas <farosas@suse.de>]

Steven Sistare <steven.sistare@oracle.com> writes:

> On 2/5/2025 4:52 PM, Steven Sistare wrote:
>> On 2/5/2025 4:28 PM, Peter Xu wrote:
>>> On Wed, Feb 05, 2025 at 12:54:01PM -0800, Steve Sistare wrote:
>>>> qmp_migrate guarantees that cpr_channel is not null for
>>>> MIG_MODE_CPR_TRANSFER when cpr_state_save is called:
>>>>
>>>>      qmp_migrate()
>>>>          if (s->parameters.mode == MIG_MODE_CPR_TRANSFER && !cpr_channel) {
>>>>              return;
>>>>          }
>>>>          cpr_state_save(cpr_channel)
>>>>
>>>> but cpr_state_save checks for mode differently before using channel,
>>>> and Coverity cannot infer that they are equivalent in outgoing QEMU,
>>>> and warns that channel may be NULL:
>>>>
>>>>      cpr_state_save(channel)
>>>>          MigMode mode = migrate_mode();
>>>>          if (mode == MIG_MODE_CPR_TRANSFER) {
>>>>              f = cpr_transfer_output(channel, errp);
>>>>
>>>> To make Coverity happy, use parameters.mode in cpr_state_save.
>>>>
>>>> Resolves: Coverity CID 1590980
>>>> Reported-by: Peter Maydell <peter.maydell@linaro.org>
>>>> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
>>>> ---
>>>>   migration/cpr.c | 3 ++-
>>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/migration/cpr.c b/migration/cpr.c
>>>> index 584b0b9..7f20bd5 100644
>>>> --- a/migration/cpr.c
>>>> +++ b/migration/cpr.c
>>>> @@ -8,6 +8,7 @@
>>>>   #include "qemu/osdep.h"
>>>>   #include "qapi/error.h"
>>>>   #include "migration/cpr.h"
>>>> +#include "migration/migration.h"
>>>>   #include "migration/misc.h"
>>>>   #include "migration/options.h"
>>>>   #include "migration/qemu-file.h"
>>>> @@ -132,7 +133,7 @@ int cpr_state_save(MigrationChannel *channel, Error **errp)
>>>>   {
>>>>       int ret;
>>>>       QEMUFile *f;
>>>> -    MigMode mode = migrate_mode();
>>>> +    MigMode mode = migrate_get_current()->parameters.mode;
>>>
>>> Are we sure this can make coverity happy?
>> 
>> It should, based on Peter Maydell's analysis, but I would appreciate
>> if he could apply and test the fix.
>> 
>>> Another more straightforward change is caching migrate mode in
>>> qmp_migrate() and also check that before invoking cpr_state_save().
>> 
>> Surely anyone would consider my one-line change to be straight forward.
>
>
> Given that Coverity complains about channel, and not mode, this is the
> most direct fix:
>
> ----------------------------------------
> diff --git a/migration/cpr.c b/migration/cpr.c
> index 59644e8..224b6ff 100644
> --- a/migration/cpr.c
> +++ b/migration/cpr.c
> @@ -160,6 +160,7 @@ int cpr_state_save(MigrationChannel *channel, Error **errp)
>       trace_cpr_state_save(MigMode_str(mode));
>
>       if (mode == MIG_MODE_CPR_TRANSFER) {
> +        g_assert(channel);
>           f = cpr_transfer_output(channel, errp);
>       } else {
>           return 0;
> -------------------------------
>
> - Steve

Queueing this^ version. Thanks