From patchwork Thu Sep 22 03:10:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 1681144 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=openvswitch.org (client-ip=140.211.166.138; helo=smtp1.osuosl.org; envelope-from=ovs-dev-bounces@openvswitch.org; receiver=) Authentication-Results: legolas.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=chromium.org header.i=@chromium.org header.a=rsa-sha256 header.s=google header.b=EefbEI0k; dkim-atps=neutral Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-384) server-digest SHA384) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4MYHXy4vW9z1yqX for ; Fri, 23 Sep 2022 00:22:10 +1000 (AEST) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 4A75E83F51; Thu, 22 Sep 2022 14:22:07 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org 4A75E83F51 Authentication-Results: smtp1.osuosl.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=chromium.org header.i=@chromium.org header.a=rsa-sha256 header.s=google header.b=EefbEI0k X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VvWtdhkfMDrm; Thu, 22 Sep 2022 14:22:03 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp1.osuosl.org (Postfix) with ESMTPS id C542883EEC; Thu, 22 Sep 2022 14:21:58 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org C542883EEC Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 4B527C0087; Thu, 22 Sep 2022 14:21:56 +0000 (UTC) X-Original-To: dev@openvswitch.org Delivered-To: ovs-dev@lists.linuxfoundation.org Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 50A3FC002D for ; Thu, 22 Sep 2022 03:10:28 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id E2D8F405E3 for ; Thu, 22 Sep 2022 03:10:26 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp2.osuosl.org E2D8F405E3 Authentication-Results: smtp2.osuosl.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.a=rsa-sha256 header.s=google header.b=EefbEI0k X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8eMOHtPQ1Ozo for ; Thu, 22 Sep 2022 03:10:25 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.8.0 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp2.osuosl.org CCDAF405FA Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by smtp2.osuosl.org (Postfix) with ESMTPS id CCDAF405FA for ; Thu, 22 Sep 2022 03:10:25 +0000 (UTC) Received: by mail-pj1-x102f.google.com with SMTP id q35-20020a17090a752600b002038d8a68fbso861264pjk.0 for ; Wed, 21 Sep 2022 20:10:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date; bh=h9cusoEVOsvIBl4L0VXSFc2MJFL0mH6lft5B/P8cXkg=; b=EefbEI0k1Fvv0iVYJuV6w/tObk4UgFVwCXCDy/bABsI3ElERV6iytXpTF/NpFdgI1O d81RNyJnc5vfQA1f6BhbuzkggUhj9QwTixgkqhyctIWzBuhtrRb6AZvcdQwcRe2lnbl1 JLox0/9IOh9NJapFOjCMAnZr4uVg2HMv5Yxdo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date; bh=h9cusoEVOsvIBl4L0VXSFc2MJFL0mH6lft5B/P8cXkg=; b=ZNJoyuFh1doVlpqP3v+pAE8R4UOOFfaRyaEONWi3TvL07Yfy0/392ZvcVQPBT8nbYr yijkh8rJcg4Ty1So3WoBqu+ZQXuG1S83UOKN+XfUb7ZvW9eogw4KU/X3vTt8LuvEG77F XAUfNvqFfYx+73dgIZkih/tRNQBvN6ugZ8cQT4oFMq6ni/y0CpDXNA0TpuL214QBsy3v xRTLt4ZRxdplz0lnxFHxkkEHa5x3dA5N8ogHPya7NS83yCKTT08ThWJFakNKaDmqAUQl adLb3LIZo6Ur+0bwsyl9uEijs4qvC0JHLmGmbSKLAsdW0EY8iapvSr21nEok/62wJDYG loqA== X-Gm-Message-State: ACrzQf1yap4Q4KB2GAd2D9OtXDM1W2Fo/CgWwXSyY9aT6mWPhuld6qJ/ 3vXi37QIbEo8l6vGkBhSeksIhQ== X-Google-Smtp-Source: AMsMyM7erk6BHrQMxxcqPheW+HKrcqt2FcPmRVEmbz5MxMnxjV9RgJfmyvf0sA3fzWftgJsc7PNdUw== X-Received: by 2002:a17:902:c205:b0:178:5083:f656 with SMTP id 5-20020a170902c20500b001785083f656mr1264667pll.81.1663816225447; Wed, 21 Sep 2022 20:10:25 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id o9-20020a170902d4c900b0016c1a1c1405sm2690393plg.222.2022.09.21.20.10.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Sep 2022 20:10:22 -0700 (PDT) From: Kees Cook To: Vlastimil Babka Date: Wed, 21 Sep 2022 20:10:02 -0700 Message-Id: <20220922031013.2150682-2-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220922031013.2150682-1-keescook@chromium.org> References: <20220922031013.2150682-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5962; h=from:subject; bh=xZ4KvmpECLGcGEsYM/zKNprXKbXd9yWPl8ziuEK6bU0=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBjK9ISH57RDxzGZ7UZialGYuMXkkODnaIpmrO6frz1 JnTSVj+JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYyvSEgAKCRCJcvTf3G3AJs0jD/ 9D8TMVp8e4DH86Ac/6txtkiLFvVFUXmWJTlIcztV3aHNeZUFgTtyJKbUyS/zmxZaIieM8uNiDl18aZ tFXG4/tQosDRpfPGTWZkPNKyVy0co9qQoJAqsQVgJijjzWaXitPIznFfMRsWJsHZkUlmSdgw7eGkue K/icTyNOfGqisB9zJ0Rt3u/9DuWH14ggoiHvu7PxwGUjRFaMvnXAAKaW1UIq9F83dyJjGUm38DADu9 4dfZCCjPjSlkFriDoF1Zl46UYapSeK6CjKINCrRxjHKe82xChD5DMqlJEXgUnMKNy0sDPpTsxq8Sda JGgN3Ry4iAbRaoNtpXRBsXwPfUk8qR3S1CYwwijhfkVjmK3DhOovAJqhsH3zX1A8DN1NawNv8K0iBn hQ6VQZGmjHr/hZoda6Rd/h98UPn+CpR5tnDV/gyX8lOcFytpbAUW/lXz0TR5Iyoto6OHwy+zO1n7AW MyqbTwIMPC7c17AKOQ8+COEl1jWv0QQyw8lCdYFsTBZ5aVwhfdqgd4NZbuYDdxUsEH81SVQQEZYqXf vGaIzaLEwq+c8FBwEDkGblzx1mqKGyz9o36hzstihC4vNVyv03Azq4elSlE2ZgKbhstadli4oCjvIt rnGXqP02zpXF4W9AgWxjdb/dO4G60VkpbWgiEbgUFW6b+Ei2xtqE09gmRfLg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 X-Mailman-Approved-At: Thu, 22 Sep 2022 14:21:51 +0000 Cc: linux-wireless@vger.kernel.org, Jacob Shin , llvm@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, Eric Dumazet , linux-hardening@vger.kernel.org, Sumit Semwal , dev@openvswitch.org, x86@kernel.org, Jesse Brandeburg , intel-wired-lan@lists.osuosl.org, David Rientjes , Miguel Ojeda , Yonghong Song , Paolo Abeni , linux-media@vger.kernel.org, Marco Elver , Kees Cook , Josef Bacik , linaro-mm-sig@lists.linaro.org, Jakub Kicinski , David Sterba , Andrew Morton , Alex Elder , Greg Kroah-Hartman , Nick Desaulniers , linux-kernel@vger.kernel.org, "David S. Miller" , Pekka Enberg , Daniel Micay , netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org, Joonsoo Kim , =?utf-8?q?Christian_K=C3=B6nig?= , linux-btrfs@vger.kernel.org Subject: [ovs-dev] [PATCH 01/12] slab: Introduce kmalloc_size_roundup() X-BeenThere: ovs-dev@openvswitch.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: ovs-dev-bounces@openvswitch.org Sender: "dev" In the effort to help the compiler reason about buffer sizes, the __alloc_size attribute was added to allocators. This improves the scope of the compiler's ability to apply CONFIG_UBSAN_BOUNDS and (in the near future) CONFIG_FORTIFY_SOURCE. For most allocations, this works well, as the vast majority of callers are not expecting to use more memory than what they asked for. There is, however, one common exception to this: anticipatory resizing of kmalloc allocations. These cases all use ksize() to determine the actual bucket size of a given allocation (e.g. 128 when 126 was asked for). This comes in two styles in the kernel: 1) An allocation has been determined to be too small, and needs to be resized. Instead of the caller choosing its own next best size, it wants to minimize the number of calls to krealloc(), so it just uses ksize() plus some additional bytes, forcing the realloc into the next bucket size, from which it can learn how large it is now. For example: data = krealloc(data, ksize(data) + 1, gfp); data_len = ksize(data); 2) The minimum size of an allocation is calculated, but since it may grow in the future, just use all the space available in the chosen bucket immediately, to avoid needing to reallocate later. A good example of this is skbuff's allocators: data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc); ... /* kmalloc(size) might give us more room than requested. * Put skb_shared_info exactly at the end of allocated zone, * to allow max possible filling before reallocation. */ osize = ksize(data); size = SKB_WITH_OVERHEAD(osize); In both cases, the "how large is the allocation?" question is answered _after_ the allocation, where the compiler hinting is not in an easy place to make the association any more. This mismatch between the compiler's view of the buffer length and the code's intention about how much it is going to actually use has already caused problems[1]. It is possible to fix this by reordering the use of the "actual size" information. We can serve the needs of users of ksize() and still have accurate buffer length hinting for the compiler by doing the bucket size calculation _before_ the allocation. Code can instead ask "how large an allocation would I get for a given size?". Introduce kmalloc_size_roundup(), to serve this function so we can start replacing the "anticipatory resizing" uses of ksize(). [1] https://github.com/ClangBuiltLinux/linux/issues/1599 https://github.com/KSPP/linux/issues/183 Cc: Vlastimil Babka Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andrew Morton Cc: linux-mm@kvack.org Signed-off-by: Kees Cook --- include/linux/slab.h | 31 +++++++++++++++++++++++++++++++ mm/slab_common.c | 17 +++++++++++++++++ 2 files changed, 48 insertions(+) diff --git a/include/linux/slab.h b/include/linux/slab.h index 0fefdf528e0d..4fc41e4ed4a2 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -188,7 +188,21 @@ void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __a void kfree(const void *objp); void kfree_sensitive(const void *objp); size_t __ksize(const void *objp); + +/** + * ksize - Report actual allocation size of associated object + * + * @objp: Pointer returned from a prior kmalloc()-family allocation. + * + * This should not be used for writing beyond the originally requested + * allocation size. Either use krealloc() or round up the allocation size + * with kmalloc_size_roundup() prior to allocation. If this is used to + * access beyond the originally requested allocation size, UBSAN_BOUNDS + * and/or FORTIFY_SOURCE may trip, since they only know about the + * originally allocated size via the __alloc_size attribute. + */ size_t ksize(const void *objp); + #ifdef CONFIG_PRINTK bool kmem_valid_obj(void *object); void kmem_dump_obj(void *object); @@ -779,6 +793,23 @@ extern void kvfree(const void *addr); extern void kvfree_sensitive(const void *addr, size_t len); unsigned int kmem_cache_size(struct kmem_cache *s); + +/** + * kmalloc_size_roundup - Report allocation bucket size for the given size + * + * @size: Number of bytes to round up from. + * + * This returns the number of bytes that would be available in a kmalloc() + * allocation of @size bytes. For example, a 126 byte request would be + * rounded up to the next sized kmalloc bucket, 128 bytes. (This is strictly + * for the general-purpose kmalloc()-based allocations, and is not for the + * pre-sized kmem_cache_alloc()-based allocations.) + * + * Use this to kmalloc() the full bucket size ahead of time instead of using + * ksize() to query the size after an allocation. + */ +unsigned int kmalloc_size_roundup(size_t size); + void __init kmem_cache_init_late(void); #if defined(CONFIG_SMP) && defined(CONFIG_SLAB) diff --git a/mm/slab_common.c b/mm/slab_common.c index 17996649cfe3..132d91a0f8c7 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -721,6 +721,23 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags) return kmalloc_caches[kmalloc_type(flags)][index]; } +unsigned int kmalloc_size_roundup(size_t size) +{ + struct kmem_cache *c; + + /* Short-circuit the 0 size case. */ + if (size == 0) + return 0; + /* Above the smaller buckets, size is a multiple of page size. */ + if (size > KMALLOC_MAX_CACHE_SIZE) + return PAGE_SIZE << get_order(size); + + /* The flags don't matter since size_index is common to all. */ + c = kmalloc_slab(size, GFP_KERNEL); + return c ? c->object_size : 0; +} +EXPORT_SYMBOL(kmalloc_size_roundup); + #ifdef CONFIG_ZONE_DMA #define KMALLOC_DMA_NAME(sz) .name[KMALLOC_DMA] = "dma-kmalloc-" #sz, #else