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 05BF119AD46; Tue, 16 Jul 2024 15:53:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721145227; cv=none; b=iwMxGUA/ITYWmLLRlLEulJRrN5pSYmxaD+Fa2G0UOE/z8/e41XAAJ8GmvIpFGLE3+TADoFlU/wuYtLc2qyuQgZhEVTdOBi0uWZ8y+xBIKOikYvaIGY/7WXAGqU+90xeR/dY83Ifeu8GVa4nRLMnatAPGsQZNtLt6EBAAPciVSS8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721145227; c=relaxed/simple; bh=YFYU7IdAo+0WOEw8UvVDAhJPdbOYjB8yIdhm5jX/yRg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=W2nkqfHpg35xeQy5qjJ5c6fsQAm9MU01w5osrcITsG+2S3YTrGf1nnKZ5FYh9hpRJ7EpakD1605tt4ZUMT8Hc9W9D43aHmNHmh7FEMSiAZN/zC2aKGTmMv0M20LaQJpnnMmgag4AgHTPpYyZpNVGBLnjC2nzbvlM5x+9CaeWaTw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vA6rdc18; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vA6rdc18" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 814D7C116B1; Tue, 16 Jul 2024 15:53:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1721145226; bh=YFYU7IdAo+0WOEw8UvVDAhJPdbOYjB8yIdhm5jX/yRg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vA6rdc18/F8RGt0Yh1qREZgLMIWk1mUT/Fa4H/EjqjPmWd2N+INhzYcUC6ZLzLg+Q 665+aOkTU3KmmE8o0sBiOJB+I4/ClbHyljIkX/dZA3A7RqKHB6MOj07e1ag1SYhvof 2KKgVmmnWADadEkg1Hsr1BFTU+FvtigXFA4u44mk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wander Lairson Costa , "Peter Zijlstra (Intel)" , Juri Lelli , Sasha Levin Subject: [PATCH 6.9 140/143] sched/deadline: Fix task_struct reference leak Date: Tue, 16 Jul 2024 17:32:16 +0200 Message-ID: <20240716152801.381029278@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240716152755.980289992@linuxfoundation.org> References: <20240716152755.980289992@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 6.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wander Lairson Costa [ Upstream commit b58652db66c910c2245f5bee7deca41c12d707b9 ] During the execution of the following stress test with linux-rt: stress-ng --cyclic 30 --timeout 30 --minimize --quiet kmemleak frequently reported a memory leak concerning the task_struct: unreferenced object 0xffff8881305b8000 (size 16136): comm "stress-ng", pid 614, jiffies 4294883961 (age 286.412s) object hex dump (first 32 bytes): 02 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 .@.............. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ debug hex dump (first 16 bytes): 53 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 S............... backtrace: [<00000000046b6790>] dup_task_struct+0x30/0x540 [<00000000c5ca0f0b>] copy_process+0x3d9/0x50e0 [<00000000ced59777>] kernel_clone+0xb0/0x770 [<00000000a50befdc>] __do_sys_clone+0xb6/0xf0 [<000000001dbf2008>] do_syscall_64+0x5d/0xf0 [<00000000552900ff>] entry_SYSCALL_64_after_hwframe+0x6e/0x76 The issue occurs in start_dl_timer(), which increments the task_struct reference count and sets a timer. The timer callback, dl_task_timer, is supposed to decrement the reference count upon expiration. However, if enqueue_task_dl() is called before the timer expires and cancels it, the reference count is not decremented, leading to the leak. This patch fixes the reference leak by ensuring the task_struct reference count is properly decremented when the timer is canceled. Fixes: feff2e65efd8 ("sched/deadline: Unthrottle PI boosted threads while enqueuing") Signed-off-by: Wander Lairson Costa Signed-off-by: Peter Zijlstra (Intel) Acked-by: Juri Lelli Link: https://lore.kernel.org/r/20240620125618.11419-1-wander@redhat.com Signed-off-by: Sasha Levin --- kernel/sched/deadline.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index a04a436af8cc4..dce51bf2d3229 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1805,8 +1805,13 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags) * The replenish timer needs to be canceled. No * problem if it fires concurrently: boosted threads * are ignored in dl_task_timer(). + * + * If the timer callback was running (hrtimer_try_to_cancel == -1), + * it will eventually call put_task_struct(). */ - hrtimer_try_to_cancel(&p->dl.dl_timer); + if (hrtimer_try_to_cancel(&p->dl.dl_timer) == 1 && + !dl_server(&p->dl)) + put_task_struct(p); p->dl.dl_throttled = 0; } } else if (!dl_prio(p->normal_prio)) { -- 2.43.0