From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 ABF032D3225; Sat, 17 Oct 2026 17:22:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792257762; cv=none; b=g0WLQgpbdp29b+WVthrpQzQIeUShg1wRnWklHiY7xZvZ2LT+QP0svaWF/80IuUiudihRHQyntKIlYfrsNh5YGN1XcDR4FCZd+CE9JbDforYSkjGayeuu4EPZ8DV2jfpGPCiD3iuTWfMjEGC1fh7EpvMDihONFoL6OL2p6kqfdM4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792257762; c=relaxed/simple; bh=AxoEAyCbllA8gFZ295PrjJ4AS71zu/dT2jAWLyydAZU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Z0o1ADpJ+N4jLStQwhkgvZrlH9Q4AgOLDs7ijeR6VC+0o61nAiTQwvk/4eLyCRAsNtIFRIu6EyrfRzXRokUqWg7SsNnXbQUk+Pr8qZt9JQlmUrVZ3uKFhtM2IbUAulfTc2SA1dZLR8NH3P1yEnEWTg4PpUIvEYM8mLfs53zfKyc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JFOSygp4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="JFOSygp4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE0141F000C4; Sat, 17 Oct 2026 17:22:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792257761; bh=+AEUMo93vX1HigjSdB31X+cLDqS/iuByV/rpOi/2xTU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JFOSygp4PcoZj0g3mNvCoUiELwjZ1J+1hAXbjL4qCEexVo0D1W3wCSGxNhbXbk4oU s/y0L2A3ukOclkSPrtiwKL1G/oc77IKT81+4sCpB0NrRExiR/a/2l/rwC8IsQaDYgM 4kXyiLFc5OyObFtYv58Mv1avMa8jdecbSu1dzWkU= 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 6.6 0620/1674] sched/deadline: Fix task_struct reference leak Date: Sat, 17 Oct 2026 17:48:12 +0200 Message-ID: <20261017160446.992068963@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160431.119607952@linuxfoundation.org> References: <20261017160431.119607952@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-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 | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 91459b664014d..4546d15419c2b 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1727,8 +1727,12 @@ 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) + put_task_struct(p); p->dl.dl_throttled = 0; } } else if (!dl_prio(p->normal_prio)) { -- 2.53.0