From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50105) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gG7Bn-00034W-HU for qemu-devel@nongnu.org; Fri, 26 Oct 2018 14:50:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gG7Bc-0001Op-0U for qemu-devel@nongnu.org; Fri, 26 Oct 2018 14:50:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57216) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gG7BY-0001Mt-9E for qemu-devel@nongnu.org; Fri, 26 Oct 2018 14:50:18 -0400 Date: Fri, 26 Oct 2018 19:50:09 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20181026185009.GB3854@work-vm> References: <20181026083620.10172-1-jialina01@baidu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181026083620.10172-1-jialina01@baidu.com> Subject: Re: [Qemu-devel] [PATCH v2] migration: avoid segmentfault when take a snapshot of a VM which being migrated List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jia Lina Cc: quintela@redhat.com, qemu-devel@nongnu.org, Chai Wen , Zhang Yu * Jia Lina (jialina01@baidu.com) wrote: > During an active background migration, snapshot will trigger a > segmentfault. As snapshot clears the "current_migration" struct > and updates "to_dst_file" before it finds out that there is a > migration task, Migration accesses the null pointer in > "current_migration" struct and qemu crashes eventually. > > Signed-off-by: Jia Lina > Signed-off-by: Chai Wen > Signed-off-by: Zhang Yu Thanks, that looks better. Reviewed-by: Dr. David Alan Gilbert > --- > migration/migration.c | 2 +- > migration/migration.h | 2 ++ > migration/savevm.c | 19 +++++++++++-------- > 3 files changed, 14 insertions(+), 9 deletions(-) > > diff --git a/migration/migration.c b/migration/migration.c > index d6ae879dc8..b5e71c7bfc 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -711,7 +711,7 @@ MigrationParameters *qmp_query_migrate_parameters(Error **errp) > * Return true if we're already in the middle of a migration > * (i.e. any of the active or setup states) > */ > -static bool migration_is_setup_or_active(int state) > +bool migration_is_setup_or_active(int state) > { > switch (state) { > case MIGRATION_STATUS_ACTIVE: > diff --git a/migration/migration.h b/migration/migration.h > index f7813f8261..e413d4d8b6 100644 > --- a/migration/migration.h > +++ b/migration/migration.h > @@ -241,6 +241,8 @@ void migrate_fd_error(MigrationState *s, const Error *error); > > void migrate_fd_connect(MigrationState *s, Error *error_in); > > +bool migration_is_setup_or_active(int state); > + > void migrate_init(MigrationState *s); > bool migration_is_blocked(Error **errp); > /* True if outgoing migration has entered postcopy phase */ > diff --git a/migration/savevm.c b/migration/savevm.c > index 2d10e45582..eeade8cb92 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -1319,21 +1319,25 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp) > MigrationState *ms = migrate_get_current(); > MigrationStatus status; > > - migrate_init(ms); > - > - ms->to_dst_file = f; > + if (migration_is_setup_or_active(ms->state) || > + ms->state == MIGRATION_STATUS_CANCELLING || > + ms->state == MIGRATION_STATUS_COLO) { > + error_setg(errp, QERR_MIGRATION_ACTIVE); > + return -EINVAL; > + } > > if (migration_is_blocked(errp)) { > - ret = -EINVAL; > - goto done; > + return -EINVAL; > } > > if (migrate_use_block()) { > error_setg(errp, "Block migration and snapshots are incompatible"); > - ret = -EINVAL; > - goto done; > + return -EINVAL; > } > > + migrate_init(ms); > + ms->to_dst_file = f; > + > qemu_mutex_unlock_iothread(); > qemu_savevm_state_header(f); > qemu_savevm_state_setup(f); > @@ -1355,7 +1359,6 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp) > error_setg_errno(errp, -ret, "Error while writing VM state"); > } > > -done: > if (ret != 0) { > status = MIGRATION_STATUS_FAILED; > } else { > -- > 2.13.2.windows.1 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK