From patchwork Thu Jan 20 20:01:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Tadeusz Struk X-Patchwork-Id: 534513 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 4E846C433FE for ; Thu, 20 Jan 2022 20:01:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377518AbiATUB6 (ORCPT ); Thu, 20 Jan 2022 15:01:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377500AbiATUB6 (ORCPT ); Thu, 20 Jan 2022 15:01:58 -0500 Received: from mail-pg1-x52f.google.com (mail-pg1-x52f.google.com [IPv6:2607:f8b0:4864:20::52f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9F61C061574 for ; Thu, 20 Jan 2022 12:01:57 -0800 (PST) Received: by mail-pg1-x52f.google.com with SMTP id r11so6195651pgr.6 for ; Thu, 20 Jan 2022 12:01:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=TinsR6fwhbMn8mnFX1YE59uVnDN8ArT+vYrOu2Poyew=; b=ZjLrcQEGPB04NxTW8f2C5j3T6ETKzqiv0H2LBpfT9SPGbhQTy8pUeaWxA+LqhCWBjh GQxpBsa8eq5HEnqF+rOxMh6h8L76HVeYRGdP7R3h8XdDJAMC9oDiJOi4CwcHZ234EDiO 46MKayb5qnUAcZTpWf7nfhCf2bQA2OeyXoFlD1onxqzIvCmPuCMZoyU7FvRj/BOxNVXb q3xluIKFUs6JJzopkpJDZmFNOf6HXQ6hIUY9ACx2sOJyVGQzSOTGY0rIsk10sDD3yBSL AfO8r68v0QrLo5sJCtUG9ObailBZiaI62+lc+XoViYMyV5djv8ACAAOyFPzJK7IH+EsG ExpA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=TinsR6fwhbMn8mnFX1YE59uVnDN8ArT+vYrOu2Poyew=; b=H3EuebLEC2qU6Ne4E9aZ+/Dgtdhn4/PhhjPn8XIcDFj5UyndZsajLmJLGWhmAsNxdF 4wObPCa0TNXLoQCPs3ANoFLC8YcWj57UevmlI49zOFhPp/O4xijxw1HeJaN6DN4LrHvm BrseckWudu7Obqwj5hncOdj84+DRqHA8PtOsutaaW1DvJsoig19X+QtXh3soku45V9oh Y2daPm3wwA/KoMsYmwKGM41XQONO8waH+qN2kLlCc8my+vwAxt0cEh3c3imomLfLRKw+ ZVwwW6phutWXmjlANiQD5WhRYjduZj+JvFeBU8CSrj/QyB+lziZS8kJrAMdEeIkdWlrr LCWw== X-Gm-Message-State: AOAM533sazdMwJJj+53WzU5QbfFm6m5rWrH6rRCLODIO/RCTv/xd/fQD TUHK2Xrf41ywJ4vxP4c0NnD0nw== X-Google-Smtp-Source: ABdhPJxBGzyGMNzupDgYFLIBpsDmpYwNhvD/X4HuX6a01w/mLd74reeYcK4cSwfdQnRitfb5IwWXLg== X-Received: by 2002:a63:774c:: with SMTP id s73mr280660pgc.473.1642708917266; Thu, 20 Jan 2022 12:01:57 -0800 (PST) Received: from localhost.localdomain ([50.39.160.154]) by smtp.gmail.com with ESMTPSA id n26sm638089pgf.49.2022.01.20.12.01.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Jan 2022 12:01:56 -0800 (PST) From: Tadeusz Struk To: peterz@infradead.org Cc: Tadeusz Struk , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Zhang Qiao , stable@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com Subject: [PATCH v2] sched/fair: Fix fault in reweight_entity Date: Thu, 20 Jan 2022 12:01:39 -0800 Message-Id: <20220120200139.118978-1-tadeusz.struk@linaro.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Syzbot found a GPF in reweight_entity(). This has been bisected to commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") There is a race between sched_post_fork() and setpriority(PRIO_PGRP) within a thread group that causes a null-ptr-deref in reweight_entity() in CFS. The scenario is that the main process spawns number of new threads, which then call setpriority(PRIO_PGRP, 0, prio), wait, and exit. For each of the new threads the copy_process() gets invoked, which adds the new task_struct to the group, and eventually calls sched_post_fork() for it. In the above scenario there is a possibility that setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread in the group that is just being created by copy_process(), and for which the sched_post_fork() has not been executed yet. This will trigger a null pointer dereference in reweight_entity(), as it will try to access the run queue pointer, which hasn't been set. This results it a crash as shown below: KASAN: null-ptr-deref in range [0x00000000000000a0-0x00000000000000a7] CPU: 0 PID: 2392 Comm: reduced_repro Not tainted 5.16.0-11201-gb42c5a161ea3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1.fc35 04/01/2014 RIP: 0010:reweight_entity+0x15d/0x440 RSP: 0018:ffffc900035dfcf8 EFLAGS: 00010006 Call Trace: reweight_task+0xde/0x1c0 set_load_weight+0x21c/0x2b0 set_user_nice.part.0+0x2d1/0x519 set_user_nice.cold+0x8/0xd set_one_prio+0x24f/0x263 __do_sys_setpriority+0x2d3/0x640 __x64_sys_setpriority+0x84/0x8b do_syscall_64+0x35/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae ---[ end trace 9dc80a9d378ed00a ]--- Before the mentioned change the cfs_rq pointer for the task has been set in sched_fork(), which is called much earlier in copy_process(), before the new task is added to the thread_group. Now it is done in the sched_post_fork(), which is called after that. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Zhang Qiao Cc: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org Link: https://syzkaller.appspot.com/bug?id=9d9c27adc674e3a7932b22b61c79a02da82cbdc1 Fixes: 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") Reported-by: syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com Signed-off-by: Tadeusz Struk --- Changes in v2: - Added a check in set_user_nice(), and return from there if the task is not fully setup instead of returning from reweight_entity() --- kernel/sched/core.c | 4 ++++ kernel/sched/sched.h | 11 +++++++++++ 2 files changed, 15 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2e4ae00e52d1..c3e74b6d595b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6897,6 +6897,10 @@ void set_user_nice(struct task_struct *p, long nice) if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE) return; + + /* Check if the task's schedule run queue is setup correctly */ + if (!task_rq_ready(p)) + return; /* * We have to be careful, if called from sys_setpriority(), * the task might be in the middle of scheduling on another CPU. diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index de53be905739..464f629bff5a 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1394,6 +1394,12 @@ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) return grp->my_q; } +/* returns true if cfs run queue is set for the task */ +static inline bool task_rq_ready(struct task_struct *p) +{ + return !!task_cfs_rq(p); +} + #else static inline struct task_struct *task_of(struct sched_entity *se) @@ -1419,6 +1425,11 @@ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) { return NULL; } + +static inline bool task_rq_ready(struct task_struct *p) +{ + return true; +} #endif extern void update_rq_clock(struct rq *rq);