From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C376BC0018A for ; Tue, 31 Oct 2023 17:07:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234925AbjJaRHi (ORCPT ); Tue, 31 Oct 2023 13:07:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236670AbjJaRHX (ORCPT ); Tue, 31 Oct 2023 13:07:23 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77E4910B for ; Tue, 31 Oct 2023 10:06:39 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0ABEC433C8; Tue, 31 Oct 2023 17:06:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1698771999; bh=v6KQtOa2LiYewbdzCudkSPD9igTHdIoQW+CpLGeWr5Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xeK/oLylLOaMnl1vNQ2jzq5vwYBO7LI8LkobEP4M5ekDsLdnE0+6xD360pausCj8z nacDjGv2HJ6t7Oyj1M5PUGIPj6t7IDExd21EqbwBYb1/Xwh5uOHBfqTxHb2Qlpws/B dFDvxYyAEXRGOIaY1uyaco+pl11o+AD3aH6BYcIc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gabriel Krisman Bertazi , Jens Axboe , Sasha Levin Subject: [PATCH 6.1 59/86] io_uring/fdinfo: lock SQ thread while retrieving thread cpu/pid Date: Tue, 31 Oct 2023 18:01:24 +0100 Message-ID: <20231031165920.417125737@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231031165918.608547597@linuxfoundation.org> References: <20231031165918.608547597@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jens Axboe commit 7644b1a1c9a7ae8ab99175989bfc8676055edb46 upstream. We could race with SQ thread exit, and if we do, we'll hit a NULL pointer dereference when the thread is cleared. Grab the SQPOLL data lock before attempting to get the task cpu and pid for fdinfo, this ensures we have a stable view of it. Cc: stable@vger.kernel.org Link: https://bugzilla.kernel.org/show_bug.cgi?id=218032 Reviewed-by: Gabriel Krisman Bertazi Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- io_uring/fdinfo.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c index 882bd56b01ed0..ea2c2ded4e412 100644 --- a/io_uring/fdinfo.c +++ b/io_uring/fdinfo.c @@ -51,7 +51,6 @@ static __cold int io_uring_show_cred(struct seq_file *m, unsigned int id, static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m) { - struct io_sq_data *sq = NULL; struct io_overflow_cqe *ocqe; struct io_rings *r = ctx->rings; unsigned int sq_mask = ctx->sq_entries - 1, cq_mask = ctx->cq_entries - 1; @@ -62,6 +61,7 @@ static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, unsigned int cq_shift = 0; unsigned int sq_shift = 0; unsigned int sq_entries, cq_entries; + int sq_pid = -1, sq_cpu = -1; bool has_lock; unsigned int i; @@ -139,13 +139,19 @@ static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, has_lock = mutex_trylock(&ctx->uring_lock); if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL)) { - sq = ctx->sq_data; - if (!sq->thread) - sq = NULL; + struct io_sq_data *sq = ctx->sq_data; + + if (mutex_trylock(&sq->lock)) { + if (sq->thread) { + sq_pid = task_pid_nr(sq->thread); + sq_cpu = task_cpu(sq->thread); + } + mutex_unlock(&sq->lock); + } } - seq_printf(m, "SqThread:\t%d\n", sq ? task_pid_nr(sq->thread) : -1); - seq_printf(m, "SqThreadCpu:\t%d\n", sq ? task_cpu(sq->thread) : -1); + seq_printf(m, "SqThread:\t%d\n", sq_pid); + seq_printf(m, "SqThreadCpu:\t%d\n", sq_cpu); seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files); for (i = 0; has_lock && i < ctx->nr_user_files; i++) { struct file *f = io_file_from_index(&ctx->file_table, i); -- 2.42.0