From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C240A4E80A0 for ; Mon, 28 Sep 2026 17:41:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790617314; cv=none; b=q7rydNexgWULArJiCqECXtrj2w/36xs8XGMkj9RBYCrVdwsROQszHME2oUfOhmHcUbz375gQUgypDdbwTlPcRnbcgs1RjopsTlnv77p8Fs9/uYgl19cuwu0hW4TBUkexblvXJPK1eQSdMIOi/cMZBJPLAs1D6OhuWShPrC1Tyq8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790617314; c=relaxed/simple; bh=ps8Vmpk8/Dvb3HvPEQ6r+gA9DsFwPpmM0auDoTT5Hck=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=rO4cOK0HYLkECgZnKSbONdV3INjylPpsmZIYT2fe1yRIEwWqmEr0cB8LW3YarIADPee6G53XyTwffVzGvLAzPFcR4GoU5TgPZ1DD9YcXZs33o9Czz1Lpwge+VN0IyEbyGD4CBSzLGQx7SuyfN9VeJyOW/hgKl61YA8a2Ut1SXME= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--smostafa.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=bQ2fSWEm; arc=none smtp.client-ip=209.85.208.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--smostafa.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="bQ2fSWEm" Received: by mail-ed1-f72.google.com with SMTP id 4fb4d7f45d1cf-6aafdd5a5f6so2747656a12.0 for ; Mon, 28 Sep 2026 10:41:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790617310; x=1791222110; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=tQQXCFUTzEuKqqGshgMGPB+3UWOKCHMCwqurMu3nBP4=; b=bQ2fSWEmzZ9zW4RPf8dbVeEhbqHUGuKVnTGanb//+7Ny1zSGO3V2gfWIzIVSQb9wHX CkXileWTB3aRfAL1e6N1z/dFnZFOb+/eyxUqzZVsdIDGIFmIJ4vyPPq3jneu6UkM9VHJ RoadS1TTDbZv3UpZTWzlJ6ztT/kDnJgNFtrBMbHePy1zRSzbxb0VBZYtOEiNkicHDeAH JQB8uqIotPU/LIguh1S4iEPrsfeZmHLBeK0Zc8aCNfrBEpFAUHGpaW6tyUEV3OSOpvAS ouO0C1hgSQoQcn1fk5LhOiOtgy2rzHGBYED7ZC50uUhjB4bg1RzpC0o5wtEpDTDnxdN9 NEfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790617310; x=1791222110; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=tQQXCFUTzEuKqqGshgMGPB+3UWOKCHMCwqurMu3nBP4=; b=o+gRcNF3xuwHRy5+Sq7ZYo1W09NHQSFiCbri3n0bsaC759xxseOU4hVvY79ttFpUoC wwfS91E5bnWuGEvYSsZvaW0Nzt1rm7NJGl92z0RBuv2e4SZ2A7xTh5v+bjVQ6PzIZxOL OpGOJrem3VNblLrG42VjA6l5mjT+i2TT8TRPW0CMVDPFFKEcotl9+MotBTstW/iJndhm iD3fWywguJl7Auyss5W5Lt0UUOadta1+2r5CcSfMxiMZIfyG9uqn2P/7qyC08Ckjcqhh FQHGzuXFWkVnqgDFuBp5SF4k/e84HnL3mPbGYzLrUib0wq9ExpcRkV8vlK5BOJZJBwQT 7FyA== X-Gm-Message-State: AFq9FYK2FrGRbgHDnHH/4YfZiFN7Bw2q2k2jGg4+ncybb0ag57zADbif z4ZQ9dpMgH6kR9IxJ7sY1xIBxMGDCE30ysvl0LOQlYs3Bnvyya+quZgRjadyqr++NcdnIMIyMVb dJIkRdj1qO3CaKZ5wfGB2z4qRSXmj3HFOc9yZT2KNGXfS++d4d4vk8Lm62GDnT9nLvneII1ohgX zFdTo3I6fey58ae4qgQvf3jb40rBoMNsN3hATZmkCyUrW3VL69zXk= X-Received: from edfz6.prod.google.com ([2002:a05:6402:a406:b0:6aa:1383:f342]) (user=smostafa job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6402:538b:b0:6aa:fc60:60d0 with SMTP id 4fb4d7f45d1cf-6aafc606c77mr6303087a12.33.1790617309305; Mon, 28 Sep 2026 10:41:49 -0700 (PDT) Date: Mon, 28 Sep 2026 17:41:09 +0000 In-Reply-To: <20260928174122.3380703-1-smostafa@google.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260928174122.3380703-1-smostafa@google.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260928174122.3380703-3-smostafa@google.com> Subject: [RFC PATCH 02/15] fork: Don't assume fully populated stack during reuse From: Mostafa Saleh To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, linux-rt-devel@lists.linux.dev Cc: corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, akpm@linux-foundation.org, urezki@gmail.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, kees@kernel.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, gustavoars@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, David Stevens , Mostafa Saleh Content-Type: text/plain; charset="UTF-8" From: David Stevens In preparation for partially populated kernel stacks, don't assume that vm_area->nr_pages matches THREAD_SIZE when clearing a stack for reuse. Note that the VA range is still THREAD_SIZE in that case but it might not be fully allocated. Signed-off-by: David Stevens [Resolve conflict and updated commit msg] Signed-off-by: Mostafa Saleh --- kernel/fork.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/fork.c b/kernel/fork.c index 2065693e762c..ec4431bf309a 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -335,11 +335,16 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) vm_area = alloc_thread_stack_node_from_cache(tsk, node); if (vm_area) { + unsigned long offset = 0; + if (memcg_charge_kernel_stack(vm_area)) { vfree(vm_area->addr); return -ENOMEM; } + if (!IS_ENABLED(CONFIG_STACK_GROWSUP)) + offset = THREAD_SIZE - vm_area->nr_pages * PAGE_SIZE; + /* Reset stack metadata. */ if (!kasan_hw_tags_enabled()) kasan_unpoison_range(vm_area->addr, THREAD_SIZE); @@ -347,7 +352,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) stack = kasan_reset_tag(vm_area->addr); /* Clear stale pointers from reused stack. */ - clear_pages(vm_area->addr, vm_area->nr_pages); + clear_pages(vm_area->addr + offset, vm_area->nr_pages); tsk->stack_vm_area = vm_area; tsk->stack = stack; -- 2.56.0.rc1.315.gc6ed9934b7-goog