Re: [Qemu-devel] [PATCH v2 1/1] qemu/migration: fix the double free problem on from_src_file

[Kevin Wolf]

Am 06.06.2017 um 07:24 hat QingFeng Hao geschrieben:
> In load_snapshot, mis->from_src_file is freed twice, the first free is by
> qemu_fclose, the second is by migration_incoming_state_destroy and
> it causes Illegal instruction exception. The fix is just to remove the
> first free.
> 
> This problem is found by qemu-iotests case 068 since commit
> "660819b migration: shut src return path unconditionally". The error is:
> 068 1s ... - output mismatch (see 068.out.bad)
>     --- tests/qemu-iotests/068.out    2017-05-06 01:00:26.417270437 +0200
>     +++ 068.out.bad   2017-06-03 13:59:55.360274640 +0200
>     @@ -6,6 +6,8 @@
>      QEMU X.Y.Z monitor - type 'help' for more information
>      (qemu) savevm 0
>      (qemu) quit
>     +./common.config: line 107: 242472 Illegal instruction     (core dumped) 
> ( if [ -n "${QEMU_NEED_PID}" ]; then
>     +    echo $BASHPID > "${QEMU_TEST_DIR}/qemu-${_QEMU_HANDLE}.pid";
>     +fi; exec "$QEMU_PROG" $QEMU_OPTIONS "$@" )
>      QEMU X.Y.Z monitor - type 'help' for more information
>     -(qemu) quit
>     -*** done
>     +(qemu) *** done
> 
> Signed-off-by: QingFeng Hao <address@hidden>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> Reviewed-by: Peter Xu <address@hidden>

Dave, as you only gave R-b rather than merging the patch, should this be
merged through the block tree?

> diff --git a/migration/savevm.c b/migration/savevm.c
> index 9c320f59d0..853e14e34e 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2290,7 +2290,6 @@ int load_snapshot(const char *name, Error **errp)
>  
>      aio_context_acquire(aio_context);
>      ret = qemu_loadvm_state(f);
> -    qemu_fclose(f);
>      aio_context_release(aio_context);
>  
>      migration_incoming_state_destroy();

Did we check other callers of migration_incoming_state_destroy()?

For example, qmp_xen_load_devices_state() looks suspicious, too.

I can't tell for postcopy_ram_listen_thread() - commit 660819b didn't
seem to remove a qemu_fclose() call there, but I can't see one left
behind either. Was the file leaked before commit 660819b or am I
missing something?

Kevin