From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f48.google.com (mail-wm1-f48.google.com [209.85.128.48]) (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 CE90E1DB951 for ; Tue, 15 Apr 2025 08:48:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744706919; cv=none; b=T9GxdOy1LftQkfEb8URXDw5kQ8Oi27LD39Lo/CSritb2wONKnuPK+a1Mh1o/ywKFZBhteX/RvkSVdLp9BijmcODQIqcfSDET+ddLEQvMUI8pQitPi+1ARQ22BphqHmKKeLcjEqq6gfppIp6vuzCUx0lEoJ/fd9mc3Fa7M1EzCuY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744706919; c=relaxed/simple; bh=YpGE9PeI6qljbIjagiXOfBb0zzsFMHdNh4gM5kYQc20=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Dd+7H8XTm4UdYR34u2xzjEeDB3Sbe5Cl6HmClsrJ55ACPBrLwg4nk8XQVoO8XMHBSmAFRjZ9+EZJVLchfxjKITovGnWNX3XmjC2nMOqJYCCVn9BzjWRG8SK5I96b52BSxWkVXzCvs68RytVWSGkXpdZNTWknlw/+zhTTvTZtflo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=BViVzzqA; arc=none smtp.client-ip=209.85.128.48 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=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="BViVzzqA" Received: by mail-wm1-f48.google.com with SMTP id 5b1f17b1804b1-43cfe808908so47195e9.0 for ; Tue, 15 Apr 2025 01:48:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1744706915; x=1745311715; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=P2dLV0t9lDObm6obO+scd0gk1JmVp4YwTv7aMmXR6dQ=; b=BViVzzqAS+RwFsvXqalo32FHBj7Ze9d2F3a6pSssFPxP4M77hI33r3HxCH1PWKEKwt 2cYZtkNcGmBk8x7gzn1nuugBvzwhpsudNmugKfKc7jmadl1E4v6vHa5BToq6A95OLMKU J1vk7NZWu6DW9DT92km1Xt/wzQGYFteE+QxQWDpMTI983t5IXFbjU/hbmD3z/L/J3t6G tzhqAGJzHEZMn8g6+W7DlXo1tw/aYqLppU33NR7au8b+N5AwhEhSadI32CjUqxiHWhVh Hl6dvlgwZ2yEh04FvU02o/NJxr5j7wvx6pYVVp7qfG8IDswB3mA1ltlmxXTMPYka94HF u9hA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744706915; x=1745311715; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=P2dLV0t9lDObm6obO+scd0gk1JmVp4YwTv7aMmXR6dQ=; b=gfksN6yQgHH5rN6F0IKKobBhvRnHnfQgzfBjyRaXUJwuTYTwcLoxtfWXm/7ijxTXpP Au61nCoIwRQgfxjQvqLGmmqGuNdS0g8Wo6iTcjasRiBA07UJhhAe6r9kBqFD15ASZkBM OqGx0mmGqGYBboG1rqeZa14KAGcwgC1kYf5FIo51LZsXBDZusmYzLLz/Q/zaWPc9QRie sbPJpu/YS4gv/i+qFIXM79rrcjBE0QuEYraim7M6PZfcLuTQkLV8nRKc3xn8siQj0Z5G CY59Ph+lWwlDHrrdjlm9ZoT3b66Etlgl2UyJO9qlThnhCf+iOEU4qgnaWqnjMA9cRPnL 2+Ww== X-Forwarded-Encrypted: i=1; AJvYcCXzQ9VtyfS9yZMJhVnbvU8JNTvGjmTNM/M6btFdkX6H904dwUreL5GQ/Vi7h/2dYVy1OTL3qENsO10KBQ4EFRQ=@vger.kernel.org X-Gm-Message-State: AOJu0Yz7yo8ewitkQ0ycumSlypP/EXw30Iw34ArS/0JckuunAIRY+T2g 5IyBSeFwXxRq6Kq0djsL73XXAk1zxMCWy88yToG2Yf7bjeVaMd3YIXYdLTKMxg== X-Gm-Gg: ASbGncteTBnytGBhJadlzmz26nCGc/z1EUZx5LuZ4NTdGIpVYyMrmSLacGlxueHHXxQ 9yzsGTDzPQGWz6CD8Uj24Rj34fEUtdKjqb3TvHPwo5xNb2qvR5xf2yMBlkxpBl5a1jcZYLRIXsx 2SRymvMnCIQkX+IvF6oL1RojzcKvluZV198+t4V9IX3/R/mGBrIsOouUsnTMU08gZj4o25sXAcQ pfTaUVam+uo5zbYIfl+M2kRh4oruxF5HNa98uCyW63YOBU3O4QjQZ2YPChO2++HwARfsGDqj+PZ jWdJyCGemHveTePcPQ3H5YfMikbQuR78ROR+KHGC+KNj4SBsz80Gk1ED7p3rt4+6vC1W0o9PBHq vPyY= X-Google-Smtp-Source: AGHT+IEw3FcKaMzh8DzK+uNK+g/Fol/Pa9NIHCybAcjdx76dEeQ3Is9Gamr39YCVdPE+Fgj9TkcRtA== X-Received: by 2002:a05:600c:4247:b0:43d:169e:4d75 with SMTP id 5b1f17b1804b1-44039657a6bmr408175e9.1.1744706914774; Tue, 15 Apr 2025 01:48:34 -0700 (PDT) Received: from google.com (202.88.205.35.bc.googleusercontent.com. [35.205.88.202]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39eaf43cb43sm13614636f8f.65.2025.04.15.01.48.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Apr 2025 01:48:34 -0700 (PDT) Date: Tue, 15 Apr 2025 08:48:30 +0000 From: Mostafa Saleh To: Andrew Morton Cc: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-hardening@vger.kernel.org, kees@kernel.org, elver@google.com, andreyknvl@gmail.com, ryabinin.a.a@gmail.com Subject: Re: [PATCH] lib/test_ubsan.c: Fix panic from test_ubsan_out_of_bounds Message-ID: References: <20250414213648.2660150-1-smostafa@google.com> <20250414170414.74f1c4e3542b1f10c8b24d90@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250414170414.74f1c4e3542b1f10c8b24d90@linux-foundation.org> On Mon, Apr 14, 2025 at 05:04:14PM -0700, Andrew Morton wrote: > On Mon, 14 Apr 2025 21:36:48 +0000 Mostafa Saleh wrote: > > > Running lib_ubsan.ko on arm64 (without CONFIG_UBSAN_TRAP) panics the > > kernel > > > > [ 31.616546] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: test_ubsan_out_of_bounds+0x158/0x158 [test_ubsan] > > [ 31.646817] CPU: 3 UID: 0 PID: 179 Comm: insmod Not tainted 6.15.0-rc2 #1 PREEMPT > > [ 31.648153] Hardware name: linux,dummy-virt (DT) > > [ 31.648970] Call trace: > > [ 31.649345] show_stack+0x18/0x24 (C) > > [ 31.650960] dump_stack_lvl+0x40/0x84 > > [ 31.651559] dump_stack+0x18/0x24 > > [ 31.652264] panic+0x138/0x3b4 > > [ 31.652812] __ktime_get_real_seconds+0x0/0x10 > > [ 31.653540] test_ubsan_load_invalid_value+0x0/0xa8 [test_ubsan] > > [ 31.654388] init_module+0x24/0xff4 [test_ubsan] > > [ 31.655077] do_one_initcall+0xd4/0x280 > > [ 31.655680] do_init_module+0x58/0x2b4 > > > > That happens because the test corrupts other data in the stack: > > 400: d5384108 mrs x8, sp_el0 > > 404: f9426d08 ldr x8, [x8, #1240] > > 408: f85f83a9 ldur x9, [x29, #-8] > > 40c: eb09011f cmp x8, x9 > > 410: 54000301 b.ne 470 // b.any > > > > As there is no guarantee the compiler will order the local variables > > as declared in the module: > > argh. > > > volatile char above[4] = { }; /* Protect surrounding memory. */ > > volatile int arr[4]; > > volatile char below[4] = { }; /* Protect surrounding memory. */ > > > > So, instead of writing out-of-bound, we can read out-of-bound which > > still triggers UBSAN but doesn't corrupt the stack. > > Would it be better to put the above three items into a struct, so we > specify the layout? Yes, that also should work, but I ran into a panic because of another problem, where the padding before and after the arr is 4 bytes, but the index is "5", which is 8 bytes out of bound. As we can only use 4/-1 as out of bounds. That should also work: diff --git a/lib/test_ubsan.c b/lib/test_ubsan.c index 8772e5edaa4f..4533e9cb52e6 100644 --- a/lib/test_ubsan.c +++ b/lib/test_ubsan.c @@ -77,18 +77,18 @@ static void test_ubsan_shift_out_of_bounds(void) static void test_ubsan_out_of_bounds(void) { - volatile int i = 4, j = 5, k = -1; - volatile char above[4] = { }; /* Protect surrounding memory. */ - volatile int arr[4]; - volatile char below[4] = { }; /* Protect surrounding memory. */ - - above[0] = below[0]; + volatile int i = 4, j = 4, k = -1; + struct { + volatile char above[4]; /* Protect surrounding memory. */ + volatile int arr[4]; + volatile char below[4]; /* Protect surrounding memory. */ + } data; UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "above"); - arr[j] = i; + data.arr[j] = i; UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "below"); - arr[k] = i; + data.arr[k] = i; } enum ubsan_test_enum { --- I can send v2 with this approach if it's better. Thanks, Mostafa > > > --- a/lib/test_ubsan.c > > +++ b/lib/test_ubsan.c > > @@ -77,18 +77,15 @@ static void test_ubsan_shift_out_of_bounds(void) > > > > static void test_ubsan_out_of_bounds(void) > > { > > - volatile int i = 4, j = 5, k = -1; > > - volatile char above[4] = { }; /* Protect surrounding memory. */ > > + volatile int j = 5, k = -1; > > + volatile int scratch[4] = { }; > > volatile int arr[4]; > > - volatile char below[4] = { }; /* Protect surrounding memory. */ > > - > > - above[0] = below[0]; > > > > UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "above"); > > - arr[j] = i; > > + scratch[1] = arr[j]; > > > > UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "below"); > > - arr[k] = i; > > + scratch[2] = arr[k]; > > } >