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bh=sa2/urw2imMu6/yzcBVCu0Uejg3i9taSytYM/VmmU4A=; b=bhdExsNkGKWcp1D3b7mCq4KeYSR9cU9c+yQI0Qr1K3BwKvNJWb1I6JZ0KetKlCPpT4bvAh 4QtPVEwh57mPQl6n1w0QI9qAr396hRiv1xLJ+lvNI9lhXoAMuL+Kw6fqKXqGnKaEIMTZ+h QbLu+npDOGIZc92BRbyzTX/wLuGbvS4= X-MC-Unique: COz6ZeamPtqVuFm_ZKEnGw-1 From: peterx@redhat.com To: qemu-devel@nongnu.org Cc: Fabiano Rosas , peterx@redhat.com Subject: [PULL 10/15] migration: Fix use-after-free of migration state object Date: Fri, 26 Jan 2024 12:17:20 +0800 Message-ID: <20240126041725.124562-11-peterx@redhat.com> In-Reply-To: <20240126041725.124562-1-peterx@redhat.com> References: <20240126041725.124562-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; 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: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.5, 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1706242781470100003 Content-Type: text/plain; charset="utf-8" From: Fabiano Rosas We're currently allowing the process_incoming_migration_bh bottom-half to run without holding a reference to the 'current_migration' object, which leads to a segmentation fault if the BH is still live after migration_shutdown() has dropped the last reference to current_migration. In my system the bug manifests as migrate_multifd() returning true when it shouldn't and multifd_load_shutdown() calling multifd_recv_terminate_threads() which crashes due to an uninitialized multifd_recv_state. Fix the issue by holding a reference to the object when scheduling the BH and dropping it before returning from the BH. The same is already done for the cleanup_bh at migrate_fd_cleanup_schedule(). Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1969 Signed-off-by: Fabiano Rosas Link: https://lore.kernel.org/r/20240119233922.32588-2-farosas@suse.de Signed-off-by: Peter Xu --- migration/migration.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/migration/migration.c b/migration/migration.c index 219447dea1..cf17b68e57 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -648,6 +648,7 @@ static void process_incoming_migration_bh(void *opaque) MIGRATION_STATUS_COMPLETED); qemu_bh_delete(mis->bh); migration_incoming_state_destroy(); + object_unref(OBJECT(migrate_get_current())); } =20 static void coroutine_fn @@ -713,6 +714,7 @@ process_incoming_migration_co(void *opaque) } =20 mis->bh =3D qemu_bh_new(process_incoming_migration_bh, mis); + object_ref(OBJECT(migrate_get_current())); qemu_bh_schedule(mis->bh); return; fail: --=20 2.43.0