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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id a8-20020a170902ecc800b001e944fc9248sm16509454plh.194.2024.04.29.12.32.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Apr 2024 12:32:55 -0700 (PDT) Date: Mon, 29 Apr 2024 15:32:52 -0400 From: Peter Xu To: Vladimir Sementsov-Ogievskiy Cc: farosas@suse.de, eblake@redhat.com, armbru@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org, yc-core@yandex-team.ru Subject: Re: [PATCH v5 3/5] migration: process_incoming_migration_co(): fix reporting s->error Message-ID: References: <20240429191426.2327225-1-vsementsov@yandex-team.ru> <20240429191426.2327225-4-vsementsov@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240429191426.2327225-4-vsementsov@yandex-team.ru> Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.987, 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_H4=0.001, RCVD_IN_MSPIKE_WL=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 On Mon, Apr 29, 2024 at 10:14:24PM +0300, Vladimir Sementsov-Ogievskiy wrote: > It's bad idea to leave critical section with error object freed, but > s->error still set, this theoretically may lead to use-after-free > crash. Let's avoid it. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > migration/migration.c | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/migration/migration.c b/migration/migration.c > index 0d26db47f7..58fd5819bc 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -732,9 +732,19 @@ static void process_incoming_migration_bh(void *opaque) > migration_incoming_state_destroy(); > } > > +static void migrate_error_free(MigrationState *s) > +{ > + QEMU_LOCK_GUARD(&s->error_mutex); > + if (s->error) { > + error_free(s->error); > + s->error = NULL; > + } > +} > + > static void coroutine_fn > process_incoming_migration_co(void *opaque) > { > + MigrationState *s = migrate_get_current(); > MigrationIncomingState *mis = migration_incoming_get_current(); > PostcopyState ps; > int ret; > @@ -779,11 +789,9 @@ process_incoming_migration_co(void *opaque) > } > > if (ret < 0) { > - MigrationState *s = migrate_get_current(); > - > if (migrate_has_error(s)) { > WITH_QEMU_LOCK_GUARD(&s->error_mutex) { > - error_report_err(s->error); > + error_report_err(error_copy(s->error)); This looks like a bugfix, agreed. > } > } > error_report("load of migration failed: %s", strerror(-ret)); > @@ -801,6 +809,7 @@ fail: > MIGRATION_STATUS_FAILED); > migration_incoming_state_destroy(); > > + migrate_error_free(s); Would migration_incoming_state_destroy() be a better place? One thing weird is we actually reuses MigrationState*'s error for incoming too, but so far it looks ok as long as QEMU can't be both src & dst. Then calling migrate_error_free even in incoming_state_destroy() looks ok. This patch still looks like containing two changes. Better split them (or just fix the bug only)? Thanks, > exit(EXIT_FAILURE); > } > > @@ -1433,15 +1442,6 @@ bool migrate_has_error(MigrationState *s) > return qatomic_read(&s->error); > } > > -static void migrate_error_free(MigrationState *s) > -{ > - QEMU_LOCK_GUARD(&s->error_mutex); > - if (s->error) { > - error_free(s->error); > - s->error = NULL; > - } > -} > - > static void migrate_fd_error(MigrationState *s, const Error *error) > { > assert(s->to_dst_file == NULL); > -- > 2.34.1 > -- Peter Xu