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bh=eLYCl+gMT4ddn1mw8JU4xXGW6AvL44IdTtwI3nWSa3s=; b=dArSd9/HT7rX4iC0YQHPlX+Wg099lstvvaHxnIdXiHAmOaGO/3Xi8HcCFmdDS15vXCyGON yC/2+bOehhHahtwTJr8+84IYS2I99eug4HbsA82mnr35S/scksatUthLWM844uX++0nkYS k6lMOfWx/BpznYrhU5ofm29lMLz7L0w= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1705707567; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eLYCl+gMT4ddn1mw8JU4xXGW6AvL44IdTtwI3nWSa3s=; b=VxzwgKPYU1IL4Y1ng9F05rH/VJtGg4Xh6NihVavlEYw7gjzdsvpp5n3NnjvnWhbTUuQv+j FmfuwXZNRVkFgdDA== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Peter Xu Subject: [PATCH 1/5] migration: Fix use-after-free of migration state object Date: Fri, 19 Jan 2024 20:39:18 -0300 Message-Id: <20240119233922.32588-2-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20240119233922.32588-1-farosas@suse.de> References: <20240119233922.32588-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Spamd-Bar: / Authentication-Results: smtp-out2.suse.de; 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envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:2; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 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, RCVD_IN_DNSWL_MED=-2.3, 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 @suse.de) X-ZM-MESSAGEID: 1705707643945100007 Content-Type: text/plain; charset="utf-8" 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(). Signed-off-by: Fabiano Rosas --- 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 2.35.3