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b=8IQZuRfEYjpNgTheWEMyW8J33+d+FIZDE5O2vW+vMw+ndmcabACb/zLUFtXrcf+NlzhVTD 3kGP2pNAz5frGTCw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 8B4B113A72; Fri, 13 Sep 2024 22:05:48 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id qERyFDy35GaQQgAAD6G6ig (envelope-from ); Fri, 13 Sep 2024 22:05:48 +0000 From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Peter Xu , Peter Maydell , qemu-stable@nongnu.org Subject: [PATCH 2/2] migration/multifd: Fix rb->receivedmap cleanup race Date: Fri, 13 Sep 2024 19:05:42 -0300 Message-Id: <20240913220542.18305-3-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20240913220542.18305-1-farosas@suse.de> References: <20240913220542.18305-1-farosas@suse.de> MIME-Version: 1.0 X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[99.99%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:email,suse.de:mid]; RCVD_TLS_ALL(0.00)[] Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:1; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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 Fix a segmentation fault in multifd when rb->receivedmap is cleared too early. After commit 5ef7e26bdb ("migration/multifd: solve zero page causing multiple page faults"), multifd started using the rb->receivedmap bitmap, which belongs to ram.c and is initialized and *freed* from the ram SaveVMHandlers. Multifd threads are live until migration_incoming_state_destroy(), which is called after qemu_loadvm_state_cleanup(), leading to a crash when accessing rb->receivedmap. process_incoming_migration_co() ... qemu_loadvm_state() multifd_nocomp_recv() qemu_loadvm_state_cleanup() ramblock_recv_bitmap_set_offset() rb->receivedmap = NULL set_bit_atomic(..., rb->receivedmap) ... migration_incoming_state_destroy() multifd_recv_cleanup() multifd_recv_terminate_threads(NULL) Move the loadvm cleanup into migration_incoming_state_destroy(), after multifd_recv_cleanup() to ensure multifd thread have already exited when rb->receivedmap is cleared. The have_listen_thread logic can now be removed because its purpose was to delay cleanup until postcopy_ram_listen_thread() had finished. CC: qemu-stable@nongnu.org Fixes: 5ef7e26bdb ("migration/multifd: solve zero page causing multiple page faults") Signed-off-by: Fabiano Rosas --- migration/migration.c | 1 + migration/migration.h | 1 - migration/savevm.c | 9 --------- 3 files changed, 1 insertion(+), 10 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index 3dea06d577..b190a574b1 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -378,6 +378,7 @@ void migration_incoming_state_destroy(void) struct MigrationIncomingState *mis = migration_incoming_get_current(); multifd_recv_cleanup(); + qemu_loadvm_state_cleanup(); if (mis->to_src_file) { /* Tell source that we are done */ diff --git a/migration/migration.h b/migration/migration.h index 38aa1402d5..20b0a5b66e 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -101,7 +101,6 @@ struct MigrationIncomingState { /* Set this when we want the fault thread to quit */ bool fault_thread_quit; - bool have_listen_thread; QemuThread listen_thread; /* For the kernel to send us notifications */ diff --git a/migration/savevm.c b/migration/savevm.c index d0759694fd..532ee5e4b0 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -2076,10 +2076,8 @@ static void *postcopy_ram_listen_thread(void *opaque) * got a bad migration state). */ migration_incoming_state_destroy(); - qemu_loadvm_state_cleanup(); rcu_unregister_thread(); - mis->have_listen_thread = false; postcopy_state_set(POSTCOPY_INCOMING_END); object_unref(OBJECT(migr)); @@ -2130,7 +2128,6 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis) return -1; } - mis->have_listen_thread = true; postcopy_thread_create(mis, &mis->listen_thread, "mig/dst/listen", postcopy_ram_listen_thread, QEMU_THREAD_DETACHED); trace_loadvm_postcopy_handle_listen("return"); @@ -2978,11 +2975,6 @@ int qemu_loadvm_state(QEMUFile *f) trace_qemu_loadvm_state_post_main(ret); - if (mis->have_listen_thread) { - /* Listen thread still going, can't clean up yet */ - return ret; - } - if (ret == 0) { ret = qemu_file_get_error(f); } @@ -3022,7 +3014,6 @@ int qemu_loadvm_state(QEMUFile *f) } } - qemu_loadvm_state_cleanup(); cpu_synchronize_all_post_init(); return ret;