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 474B62FF676; Wed, 26 Nov 2025 15:12:29 +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=1764169950; cv=none; b=U+UhvvyHFNEgDVqOot7KuSfhRxm4cUYe3Ug8ShTBuWdUlfv/0euGJOViVd6PtPyoCX4CD4lABHWKVHhfkQXeO+R9txzdZdbxc55LDgVHeXUoRfJcgpWRVDxG+IIjDRFsxvcd+LHhGWovzJmDkLPwTymPw+qG1gU2L20pnI6E3CE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764169950; c=relaxed/simple; bh=A31ZEtB8hXgwmnRmCuYTs0YXUNocajsrU+V31FS5PcQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IWVD3neXR1AG4cRySF90pcZGse/coFKGF8L/JndwbSRzDlwnRLU1gY/qf8Q7R7yRAowUhTfmHXWKkJjC4OmCYJi1kpNetaJKVp05IUQyFgZ4aa+t9DelNlIbm5HK60AtLhn780MwvWRmUx4cWErCB3MWXn/G9xmgCWnELaaYIlE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BymReTMg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BymReTMg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 468F9C4CEF7; Wed, 26 Nov 2025 15:12:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764169949; bh=A31ZEtB8hXgwmnRmCuYTs0YXUNocajsrU+V31FS5PcQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BymReTMgbvFervNxB8f5k+j8RwfG6V71WiKCc0ukKREmcVSt/35mtWiBqV4bRcgso Zd5qN7TYdy4CkHaoA73q92T8eIQrX89FkTEt7iM0wU0gOuWqwz/nTn3l2Zh7zxdvi2 oq38RpQSAEuwBYGPre2TFhLKY8EUYVP83x9yl6KP3XDc1Ty2vh+M6W6K4H8f07k+rx fTEejYRkb+pZvlz0J9BdZnbf7ufgEsLYKtwqk5uMDdWMHhMfjOV7knTA7VTXLuZqFE nVUZ8KW/UMSGXSNQIbJDAOiUWcG+7RUnSvNHuKKqVHksGmmFJX7GVCYNt5e/SpUat5 pxombUnx+2/og== Date: Wed, 26 Nov 2025 16:12:23 +0100 From: Helge Deller To: david laight Cc: Helge Deller , John Johansen , John Paul Adrian Glaubitz , linux-kernel@vger.kernel.org, apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, linux-parisc@vger.kernel.org Subject: Re: [PATCH 0/2] apparmor unaligned memory fixes Message-ID: References: <90513f85cc8d060ebccd3972cc7709e4b6f13f34.camel@physik.fu-berlin.de> <20251126104444.29002552@pumpkin> <4034ad19-8e09-440c-a042-a66a488c048b@gmx.de> <20251126142201.27e23076@pumpkin> Precedence: bulk X-Mailing-List: linux-kernel@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: <20251126142201.27e23076@pumpkin> * david laight : > On Wed, 26 Nov 2025 12:03:03 +0100 > Helge Deller wrote: > > > On 11/26/25 11:44, david laight wrote: > ... > > >> diff --git a/security/apparmor/match.c b/security/apparmor/match.c > > >> index 26e82ba879d44..3dcc342337aca 100644 > > >> --- a/security/apparmor/match.c > > >> +++ b/security/apparmor/match.c > > >> @@ -71,10 +71,10 @@ static struct table_header *unpack_table(char *blob, size_t bsize) > > >> u8, u8, byte_to_byte); > > > > > > Is that that just memcpy() ? > > > > No, it's memcpy() only on big-endian machines. > > You've misread the quoting... > The 'data8' case that was only half there is a memcpy(). > > > On little-endian machines it converts from big-endian > > 16/32-bit ints to little-endian 16/32-bit ints. > > > > But I see some potential for optimization here: > > a) on big-endian machines just use memcpy() > > true > > > b) on little-endian machines use memcpy() to copy from possibly-unaligned > > memory to then known-to-be-aligned destination. Then use a loop with > > be32_to_cpu() instead of get_unaligned_xx() as it's faster. > > There is a function that does a loop byteswap of a buffer - no reason > to re-invent it. I assumed there must be something, but I did not see it. Which one? > But I doubt it is always (if ever) faster to do a copy and then byteswap. > The loop control and extra memory accesses kill performance. Yes, you are probably right. > Not that I've seen a fast get_unaligned() - I don't think gcc or clang > generate optimal code - For LE I think it is something like: > low = *(addr & ~3); > high = *((addr + 3) & ~3); > shift = (addr & 3) * 8; > value = low << shift | high >> (32 - shift); > Note that it is only 2 aligned memory reads - even for 64bit. Ok, then maybe we should keep it simple like this patch: [PATCH v2] apparmor: Optimize table creation from possibly unaligned memory Source blob may come from userspace and might be unaligned. Try to optize the copying process by avoiding unaligned memory accesses. Signed-off-by: Helge Deller diff --git a/security/apparmor/include/match.h b/security/apparmor/include/match.h index 1fbe82f5021b..386da2023d50 100644 --- a/security/apparmor/include/match.h +++ b/security/apparmor/include/match.h @@ -104,16 +104,20 @@ struct aa_dfa { struct table_header *tables[YYTD_ID_TSIZE]; }; -#define byte_to_byte(X) (X) +#define byte_to_byte(X) (*(X)) #define UNPACK_ARRAY(TABLE, BLOB, LEN, TTYPE, BTYPE, NTOHX) \ do { \ typeof(LEN) __i; \ TTYPE *__t = (TTYPE *) TABLE; \ BTYPE *__b = (BTYPE *) BLOB; \ - for (__i = 0; __i < LEN; __i++) { \ - __t[__i] = NTOHX(__b[__i]); \ - } \ + BUILD_BUG_ON(sizeof(TTYPE) != sizeof(BTYPE)); \ + if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) || sizeof(BTYPE) == 1) \ + memcpy(__t, __b, (LEN) * sizeof(BTYPE)); \ + else /* copy & convert convert from big-endian */ \ + for (__i = 0; __i < LEN; __i++) { \ + __t[__i] = NTOHX(&__b[__i]); \ + } \ } while (0) static inline size_t table_size(size_t len, size_t el_size) diff --git a/security/apparmor/match.c b/security/apparmor/match.c index c5a91600842a..13e2f6873329 100644 --- a/security/apparmor/match.c +++ b/security/apparmor/match.c @@ -15,6 +15,7 @@ #include #include #include +#include #include "include/lib.h" #include "include/match.h" @@ -70,10 +71,10 @@ static struct table_header *unpack_table(char *blob, size_t bsize) u8, u8, byte_to_byte); else if (th.td_flags == YYTD_DATA16) UNPACK_ARRAY(table->td_data, blob, th.td_lolen, - u16, __be16, be16_to_cpu); + u16, __be16, get_unaligned_be16); else if (th.td_flags == YYTD_DATA32) UNPACK_ARRAY(table->td_data, blob, th.td_lolen, - u32, __be32, be32_to_cpu); + u32, __be32, get_unaligned_be32); else goto fail; /* if table was vmalloced make sure the page tables are synced