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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6ce009fcd0esm41746716d6.132.2024.10.23.11.02.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Oct 2024 11:02:20 -0700 (PDT) From: Peter Xu To: qemu-devel@nongnu.org Cc: peterx@redhat.com, Alex Williamson , Fabiano Rosas , Avihai Horon , =?utf-8?q?C=C3=A9dric_Le_Goater?= Subject: [PATCH v2 2/4] migration: Reset current_migration properly Date: Wed, 23 Oct 2024 14:02:14 -0400 Message-ID: <20241023180216.1072575-3-peterx@redhat.com> X-Mailer: git-send-email 2.45.0 In-Reply-To: <20241023180216.1072575-1-peterx@redhat.com> References: <20241023180216.1072575-1-peterx@redhat.com> MIME-Version: 1.0 Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.263, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org current_migration is never reset, even if the migration object is freed already. It means anyone references that can trigger UAF and it'll be hard to debug. Properly clear the pointer now, so far by doing it in the finalize() (as we know there's only one instance of it). Add a TODO entry for it showing that we can do better in the future. To make it clear, also initialize the variable in the instance_init() so it's very well paired at least. Signed-off-by: Peter Xu --- migration/migration.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index bcb735869b..a82297db0f 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -232,9 +232,9 @@ static int migration_stop_vm(MigrationState *s, RunState state) void migration_object_init(void) { - /* This can only be called once. */ - assert(!current_migration); - current_migration = MIGRATION_OBJ(object_new(TYPE_MIGRATION)); + MIGRATION_OBJ(object_new(TYPE_MIGRATION)); + /* This should be set when initialize the object */ + assert(current_migration); /* * Init the migrate incoming object as well no matter whether @@ -3877,12 +3877,31 @@ static void migration_instance_finalize(Object *obj) qemu_sem_destroy(&ms->rp_state.rp_pong_acks); qemu_sem_destroy(&ms->postcopy_qemufile_src_sem); error_free(ms->error); + + /* + * We know we only have one intance of migration, and when reaching + * here it means migration object is gone. Clear the global reference + * to reflect that. + */ + current_migration = NULL; } static void migration_instance_init(Object *obj) { MigrationState *ms = MIGRATION_OBJ(obj); + /* + * There can only be one migration object globally. Keep a record of + * the pointer in current_migration, which will be reset after the + * object finalize(). + * + * TODO: after migration/ code can always take a MigrationObject* + * pointer all over the place, logically we can drop current_migration + * variable. + */ + assert(!current_migration); + current_migration = ms; + ms->state = MIGRATION_STATUS_NONE; ms->mbps = -1; ms->pages_per_second = -1;