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a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1692195918; 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=jAsBqbZmyUB1R931rGfF3+iNeAKRaD7BagsRZjWBM0I=; b=bgUKneSOFHz2OWc7CwozNOIs9zhLHS1ivFbvAeZtqFzbwUUgj7mxMju7FI+KhgSfZVsuZG Xk6/S1iCE7yfAaDg== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Juan Quintela , Peter Xu , Wei Wang , Leonardo Bras Subject: [PATCH v4 2/8] migration: Fix possible races when shutting down the return path Date: Wed, 16 Aug 2023 11:25:04 -0300 Message-Id: <20230816142510.5637-3-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20230816142510.5637-1-farosas@suse.de> References: <20230816142510.5637-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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=195.135.220.28; envelope-from=farosas@suse.de; helo=smtp-out1.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 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: 1692195949664100001 Content-Type: text/plain; charset="utf-8" We cannot call qemu_file_shutdown() on the return path file without taking the file lock. The return path thread could be running it's cleanup code and have just cleared the from_dst_file pointer. Checking ms->to_dst_file for errors could also race with migrate_fd_cleanup() which clears the to_dst_file pointer. Protect both accesses by taking the file lock. This was caught by inspection, it should be rare, but the next patches will start calling this code from other places, so let's do the correct thing. Signed-off-by: Fabiano Rosas Reviewed-by: Peter Xu --- migration/migration.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index f88c86079c..85c171f32c 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -2052,17 +2052,18 @@ static int open_return_path_on_source(MigrationStat= e *ms, static int await_return_path_close_on_source(MigrationState *ms) { /* - * If this is a normal exit then the destination will send a SHUT and = the - * rp_thread will exit, however if there's an error we need to cause - * it to exit. + * If this is a normal exit then the destination will send a SHUT + * and the rp_thread will exit, however if there's an error we + * need to cause it to exit. shutdown(2), if we have it, will + * cause it to unblock if it's stuck waiting for the destination. */ - if (qemu_file_get_error(ms->to_dst_file) && ms->rp_state.from_dst_file= ) { - /* - * shutdown(2), if we have it, will cause it to unblock if it's st= uck - * waiting for the destination. - */ - qemu_file_shutdown(ms->rp_state.from_dst_file); + WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) { + if (ms->to_dst_file && ms->rp_state.from_dst_file && + qemu_file_get_error(ms->to_dst_file)) { + qemu_file_shutdown(ms->rp_state.from_dst_file); + } } + trace_await_return_path_close_on_source_joining(); qemu_thread_join(&ms->rp_state.rp_thread); ms->rp_state.rp_thread_created =3D false; --=20 2.35.3