From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 256B5E548; Mon, 11 Dec 2023 18:56:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="HP1wU1oW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9EB3BC433C8; Mon, 11 Dec 2023 18:56:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1702321012; bh=VsKPg+CnHSrkc2puV0krDQabHkF2wVAOCZslqjPdSLc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HP1wU1oW6rCKrOPjip3vZIIAGuU9oGKZDYkGvujlA+Xwyz1PWL0ND+14v6J6OcGkX O+MrMY9nAV606HEsDJ/BRo6ChvdZxM0tkZGQA8WnFUgrjf0OCj3mFttAJs7xDd33X9 yagoWvip5RbsAWr0mc+H17Vwp8H/cCPXgZTOAiAk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jann Horn , Pavel Begunkov , Jens Axboe Subject: [PATCH 5.15 078/141] io_uring: fix mutex_unlock with unreferenced ctx Date: Mon, 11 Dec 2023 19:22:17 +0100 Message-ID: <20231211182029.936971617@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231211182026.503492284@linuxfoundation.org> References: <20231211182026.503492284@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pavel Begunkov commit f7b32e785042d2357c5abc23ca6db1b92c91a070 upstream. Callers of mutex_unlock() have to make sure that the mutex stays alive for the whole duration of the function call. For io_uring that means that the following pattern is not valid unless we ensure that the context outlives the mutex_unlock() call. mutex_lock(&ctx->uring_lock); req_put(req); // typically via io_req_task_submit() mutex_unlock(&ctx->uring_lock); Most contexts are fine: io-wq pins requests, syscalls hold the file, task works are taking ctx references and so on. However, the task work fallback path doesn't follow the rule. Cc: Fixes: 04fc6c802d ("io_uring: save ctx put/get for task_work submit") Reported-by: Jann Horn Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/io-uring/CAG48ez3xSoYb+45f1RLtktROJrpiDQ1otNvdR+YLQf7m+Krj5Q@mail.gmail.com/ Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- io_uring/io_uring.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2601,6 +2601,7 @@ static void io_iopoll_try_reap_events(st if (!(ctx->flags & IORING_SETUP_IOPOLL)) return; + percpu_ref_get(&ctx->refs); mutex_lock(&ctx->uring_lock); while (!list_empty(&ctx->iopoll_list)) { unsigned int nr_events = 0; @@ -2622,6 +2623,7 @@ static void io_iopoll_try_reap_events(st } } mutex_unlock(&ctx->uring_lock); + percpu_ref_put(&ctx->refs); } static int io_iopoll_check(struct io_ring_ctx *ctx, long min) @@ -9771,12 +9773,7 @@ static void io_ring_exit_work(struct wor init_completion(&exit.completion); init_task_work(&exit.task_work, io_tctx_exit_cb); exit.ctx = ctx; - /* - * Some may use context even when all refs and requests have been put, - * and they are free to do so while still holding uring_lock or - * completion_lock, see io_req_task_submit(). Apart from other work, - * this lock/unlock section also waits them to finish. - */ + mutex_lock(&ctx->uring_lock); while (!list_empty(&ctx->tctx_list)) { WARN_ON_ONCE(time_after(jiffies, timeout));