From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 64F9FCA0EC6 for ; Mon, 11 Sep 2023 21:40:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350400AbjIKVh5 (ORCPT ); Mon, 11 Sep 2023 17:37:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240915AbjIKO5S (ORCPT ); Mon, 11 Sep 2023 10:57:18 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 60ECCE4D for ; Mon, 11 Sep 2023 07:57:12 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-594e1154756so49284357b3.2 for ; Mon, 11 Sep 2023 07:57:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1694444231; x=1695049031; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=6iMPMRaHZZkPt2h2lba04yggcsYBY9dzA07C/TArg4s=; b=DA+FPVCqzC3xiD5dy2DUIeiaA8L+U42vPKtmpUtK4TOA3QzV5EqoTpziI/REVP6OM9 LZSpVvCZyUPfewXL9pJGJoPGt0EEZc86uV9QnWQA3He7eE6xf3I+ersJwTCnjRVEBUg4 Qp76AClhZaJlulIlV4HyiJjHOTqVkSWqkG9300uzRUXEoP4qUi0bkcFbyvMj7pd2bXoE nBAl9GFtOraHy6dufasOTXW1YU5cfcouhOojvgxiNW5HlmQlD3UmzJ6XQTSImL8eaVxx vWdkKazdNFOy2ekPqzsohwdJeVqbyXvVCo+sMbtZyTrnp+NrQ51qrr4uv7/pYL/sAynq c21Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1694444231; x=1695049031; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=6iMPMRaHZZkPt2h2lba04yggcsYBY9dzA07C/TArg4s=; b=D3IGNsJyhTr9iFlbffPDlUYH3yi1lTHdbeEp1C22LusVE/K5XU7MD/HpJHtio0bllN XooSp+t/lGVyy2aN0dyiW/EBPUu2x1avawTOLckJFegDawoGmLT0pPEGl2dl1hlg52Lr 2zQZJjBtPNp2Kfy2QtrE5HLpjMVPWrpSQfk3B2G4CPi4Q7ZM4YT0Qyf4L6MAxBm/PHLv Xp2+UmN9pVtHf2cNtfheiSPGQLO2+zHZbpCHQTGpoxYtCywfrOUq5CX7CBfAtP2r7bv/ wtEpCvPXMtl4nFPmhC5WNdR5/Ktc5DBbskzA64qDiismJoQ3w/yabBGgkm4eKfkyHI0n lSaw== X-Gm-Message-State: AOJu0YyYTrbp8Q7GxbWZE74byTo0VZ9dtLtVYFWeOF8DQXUEIGTD3bF9 sgjAb4a/gYVesD8MaPtYdQErcvQc4uQ= X-Google-Smtp-Source: AGHT+IEE/n86D7W4BtYVWvhxMGGLZDAbWRkUH6Etb6BUe2tQGb6wjCu5rOgyHRKUX+nMOOSbojbh9HnT304= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:62e7:6658:cb4:b858]) (user=glider job=sendgmr) by 2002:a81:b706:0:b0:58c:74ec:339b with SMTP id v6-20020a81b706000000b0058c74ec339bmr231210ywh.1.1694444231601; Mon, 11 Sep 2023 07:57:11 -0700 (PDT) Date: Mon, 11 Sep 2023 16:56:59 +0200 Mime-Version: 1.0 X-Mailer: git-send-email 2.42.0.283.g2d96d420d3-goog Message-ID: <20230911145702.2663753-1-glider@google.com> Subject: [PATCH v2 1/4] kmsan: simplify kmsan_internal_memmove_metadata() From: Alexander Potapenko To: glider@google.com, dvyukov@google.com, elver@google.com, akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kmsan_internal_memmove_metadata() is the function that implements copying metadata every time memcpy()/memmove() is called. Because shadow memory stores 1 byte per each byte of kernel memory, copying the shadow is trivial and can be done by a single memmove() call. Origins, on the other hand, are stored as 4-byte values corresponding to every aligned 4 bytes of kernel memory. Therefore, if either the source or the destination of kmsan_internal_memmove_metadata() is unaligned, the number of origin slots corresponding to the source or destination may differ: 1) memcpy(0xffff888080a00000, 0xffff888080900000, 4) copies 1 origin slot into 1 origin slot: src (0xffff888080900000): xxxx src origins: o111 dst (0xffff888080a00000): xxxx dst origins: o111 2) memcpy(0xffff888080a00001, 0xffff888080900000, 4) copies 1 origin slot into 2 origin slots: src (0xffff888080900000): xxxx src origins: o111 dst (0xffff888080a00000): .xxx x... dst origins: o111 o111 3) memcpy(0xffff888080a00000, 0xffff888080900001, 4) copies 2 origin slots into 1 origin slot: src (0xffff888080900000): .xxx x... src origins: o111 o222 dst (0xffff888080a00000): xxxx dst origins: o111 (or o222) Previously, kmsan_internal_memmove_metadata() tried to solve this problem by copying min(src_slots, dst_slots) as is and cloning the missing slot on one of the ends, if needed. This was error-prone even in the simple cases where 4 bytes were copied, and did not account for situations where the total number of nonzero origin slots could have increased by more than one after copying: memcpy(0xffff888080a00000, 0xffff888080900002, 8) src (0xffff888080900002): ..xx .... xx.. src origins: o111 0000 o222 dst (0xffff888080a00000): xx.. ..xx o111 0000 (or 0000 o222) The new implementation simply copies the shadow byte by byte, and updates the corresponding origin slot, if the shadow byte is nonzero. This approach can handle complex cases with mixed initialized and uninitialized bytes. Similarly to KMSAN inline instrumentation, latter writes to bytes sharing the same origin slots take precedence. Signed-off-by: Alexander Potapenko Fixes: f80be4571b19 ("kmsan: add KMSAN runtime core") Acked-by: Marco Elver --- mm/kmsan/core.c | 127 ++++++++++++------------------------------------ 1 file changed, 31 insertions(+), 96 deletions(-) diff --git a/mm/kmsan/core.c b/mm/kmsan/core.c index 3adb4c1d3b193..c19f47af04241 100644 --- a/mm/kmsan/core.c +++ b/mm/kmsan/core.c @@ -83,131 +83,66 @@ depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags, /* Copy the metadata following the memmove() behavior. */ void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n) { + depot_stack_handle_t prev_old_origin = 0, prev_new_origin = 0; + int i, iter, step, src_off, dst_off, oiter_src, oiter_dst; depot_stack_handle_t old_origin = 0, new_origin = 0; - int src_slots, dst_slots, i, iter, step, skip_bits; depot_stack_handle_t *origin_src, *origin_dst; - void *shadow_src, *shadow_dst; - u32 *align_shadow_src, shadow; + u8 *shadow_src, *shadow_dst; + u32 *align_shadow_dst; bool backwards; shadow_dst = kmsan_get_metadata(dst, KMSAN_META_SHADOW); if (!shadow_dst) return; KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(dst, n)); + align_shadow_dst = + (u32 *)ALIGN_DOWN((u64)shadow_dst, KMSAN_ORIGIN_SIZE); shadow_src = kmsan_get_metadata(src, KMSAN_META_SHADOW); if (!shadow_src) { - /* - * @src is untracked: zero out destination shadow, ignore the - * origins, we're done. - */ - __memset(shadow_dst, 0, n); + /* @src is untracked: mark @dst as initialized. */ + kmsan_internal_unpoison_memory(dst, n, /*checked*/ false); return; } KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(src, n)); - __memmove(shadow_dst, shadow_src, n); - origin_dst = kmsan_get_metadata(dst, KMSAN_META_ORIGIN); origin_src = kmsan_get_metadata(src, KMSAN_META_ORIGIN); KMSAN_WARN_ON(!origin_dst || !origin_src); - src_slots = (ALIGN((u64)src + n, KMSAN_ORIGIN_SIZE) - - ALIGN_DOWN((u64)src, KMSAN_ORIGIN_SIZE)) / - KMSAN_ORIGIN_SIZE; - dst_slots = (ALIGN((u64)dst + n, KMSAN_ORIGIN_SIZE) - - ALIGN_DOWN((u64)dst, KMSAN_ORIGIN_SIZE)) / - KMSAN_ORIGIN_SIZE; - KMSAN_WARN_ON((src_slots < 1) || (dst_slots < 1)); - KMSAN_WARN_ON((src_slots - dst_slots > 1) || - (dst_slots - src_slots < -1)); backwards = dst > src; - i = backwards ? min(src_slots, dst_slots) - 1 : 0; - iter = backwards ? -1 : 1; - - align_shadow_src = - (u32 *)ALIGN_DOWN((u64)shadow_src, KMSAN_ORIGIN_SIZE); - for (step = 0; step < min(src_slots, dst_slots); step++, i += iter) { - KMSAN_WARN_ON(i < 0); - shadow = align_shadow_src[i]; - if (i == 0) { - /* - * If @src isn't aligned on KMSAN_ORIGIN_SIZE, don't - * look at the first @src % KMSAN_ORIGIN_SIZE bytes - * of the first shadow slot. - */ - skip_bits = ((u64)src % KMSAN_ORIGIN_SIZE) * 8; - shadow = (shadow >> skip_bits) << skip_bits; + step = backwards ? -1 : 1; + iter = backwards ? n - 1 : 0; + src_off = (u64)src % KMSAN_ORIGIN_SIZE; + dst_off = (u64)dst % KMSAN_ORIGIN_SIZE; + + /* Copy shadow bytes one by one, updating the origins if necessary. */ + for (i = 0; i < n; i++, iter += step) { + oiter_src = (iter + src_off) / KMSAN_ORIGIN_SIZE; + oiter_dst = (iter + dst_off) / KMSAN_ORIGIN_SIZE; + if (!shadow_src[iter]) { + shadow_dst[iter] = 0; + if (!align_shadow_dst[oiter_dst]) + origin_dst[oiter_dst] = 0; + continue; } - if (i == src_slots - 1) { - /* - * If @src + n isn't aligned on - * KMSAN_ORIGIN_SIZE, don't look at the last - * (@src + n) % KMSAN_ORIGIN_SIZE bytes of the - * last shadow slot. - */ - skip_bits = (((u64)src + n) % KMSAN_ORIGIN_SIZE) * 8; - shadow = (shadow << skip_bits) >> skip_bits; - } - /* - * Overwrite the origin only if the corresponding - * shadow is nonempty. - */ - if (origin_src[i] && (origin_src[i] != old_origin) && shadow) { - old_origin = origin_src[i]; - new_origin = kmsan_internal_chain_origin(old_origin); + shadow_dst[iter] = shadow_src[iter]; + old_origin = origin_src[oiter_src]; + if (old_origin == prev_old_origin) + new_origin = prev_new_origin; + else { /* * kmsan_internal_chain_origin() may return * NULL, but we don't want to lose the previous * origin value. */ + new_origin = kmsan_internal_chain_origin(old_origin); if (!new_origin) new_origin = old_origin; } - if (shadow) - origin_dst[i] = new_origin; - else - origin_dst[i] = 0; - } - /* - * If dst_slots is greater than src_slots (i.e. - * dst_slots == src_slots + 1), there is an extra origin slot at the - * beginning or end of the destination buffer, for which we take the - * origin from the previous slot. - * This is only done if the part of the source shadow corresponding to - * slot is non-zero. - * - * E.g. if we copy 8 aligned bytes that are marked as uninitialized - * and have origins o111 and o222, to an unaligned buffer with offset 1, - * these two origins are copied to three origin slots, so one of then - * needs to be duplicated, depending on the copy direction (@backwards) - * - * src shadow: |uuuu|uuuu|....| - * src origin: |o111|o222|....| - * - * backwards = 0: - * dst shadow: |.uuu|uuuu|u...| - * dst origin: |....|o111|o222| - fill the empty slot with o111 - * backwards = 1: - * dst shadow: |.uuu|uuuu|u...| - * dst origin: |o111|o222|....| - fill the empty slot with o222 - */ - if (src_slots < dst_slots) { - if (backwards) { - shadow = align_shadow_src[src_slots - 1]; - skip_bits = (((u64)dst + n) % KMSAN_ORIGIN_SIZE) * 8; - shadow = (shadow << skip_bits) >> skip_bits; - if (shadow) - /* src_slots > 0, therefore dst_slots is at least 2 */ - origin_dst[dst_slots - 1] = - origin_dst[dst_slots - 2]; - } else { - shadow = align_shadow_src[0]; - skip_bits = ((u64)dst % KMSAN_ORIGIN_SIZE) * 8; - shadow = (shadow >> skip_bits) << skip_bits; - if (shadow) - origin_dst[0] = origin_dst[1]; - } + origin_dst[oiter_dst] = new_origin; + prev_new_origin = new_origin; + prev_old_origin = old_origin; } } -- 2.42.0.283.g2d96d420d3-goog