From nobody Sat Feb 7 17:09:54 2026 Received: from mail-pg1-f180.google.com (mail-pg1-f180.google.com [209.85.215.180]) (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 81A1254273 for ; Fri, 1 Mar 2024 23:09:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709334566; cv=none; b=L3RMFdcTWVAZ6sCmz2ml1+Y+0/gYtCrbTgt52HmhTt1CThuG5IeyZ9HB58MMACaOpwwE8iBl6BZJxi/a4xsPR8SJCv1inf9/+HqZMT40grQF7znhLdQbJ3VnMgkrKy3L8MRAA2q/PrN0spdG5gqnoYEcqUybXZ51zcCxR8YBLQs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709334566; c=relaxed/simple; bh=UEhiR0jtRmVH9tnub8DcCdKOCm+M1Xk2IcoEwXI0hN0=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=q8ndyCCX9F+XhXPm36bjImD0ESSTe6/Ykn0s+zBJNl3ULc/s9WUXKHOqNwtoS0wZvD6wugHurMLTRTanexzV1XSuw/eydmV7RIGBFSmZWvYTGRYz53Xx3keqfjenHVCnycxKzhUUmxpJL8ScxUo54KEzbTF9XB5dsHsB1vVdBJk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=RncOxs9e; arc=none smtp.client-ip=209.85.215.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="RncOxs9e" Received: by mail-pg1-f180.google.com with SMTP id 41be03b00d2f7-517ab9a4a13so2137840a12.1 for ; Fri, 01 Mar 2024 15:09:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1709334564; x=1709939364; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=lOZA8JIxILGqvM6CHZHHbg/5cKwIFudQyVhIk0Vrhx8=; b=RncOxs9e29yBeOOKMweBuyWnCe1byN5gX91pSCGItDYd3vWTAK92WFgWEy+M/sWv7i DkL6xKhWqv9uQlFVz8K8MD9L1nbgPiieVkfu/prsQ/1HU2Wfr2RE71OeUR16pHX97msQ bZ98ESzgyxP8j9W/5gPy1vhUTrroFVnrkEtu7b0Nn5AiWMw0bU9ID1TcCZwF3BJEeOww KQzpIPs887rdRwcnlUq+/ESekzW14f/8ShKkl2hnoXDiR/3Nxg0nXQ7VgokJ7CDOnZ7n 3+VcAzDRiqOdPVCIXKLSo3mZshoti0AqWDfrhy44lX9qYtg3Iw13KxMqqus5pFLLJEQz 5OHw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709334564; x=1709939364; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=lOZA8JIxILGqvM6CHZHHbg/5cKwIFudQyVhIk0Vrhx8=; b=GYvSKo4jonNAY3O829TDtBze3yVqXlII0yQgd2qFGFwF7+R/8iyaLSPlGdkObn7rqj wLjMNMQCQdWyYk/XwTvxOE+jfq67u+S6unAY64KxTSBl+VL+kOqF4D4tP8sZcl+W1mDa WTBOp2PDZiQ5eQjnkfR2S8XvNZQmpfD4zdWOISQUMs6dlfACXtzBpy2uHP4p3D4Va893 6pyjue41iJffH9QkooW1SfSqvkx2PafisjEPenYtIzACMUiq/TUvO2G48LscBM9hKB4+ pDOz8KPb8kOmVwWBFlgjJaulBOKsrSB+pkiP3aCUWhIWOxAakB1YWr9M9xQAOrAiDNN2 s2Lg== X-Forwarded-Encrypted: i=1; AJvYcCXJrpmUs4c1C1SW8KtJoP+sByw7fuowxCMBOZmwy9MIVA2OrCaeZK6eq6M5kYrW8IKJC6a1G1z5UKwaRuq7AXswZAd0u10ZkGyhySKF X-Gm-Message-State: AOJu0YygzZzslUTTwr7gDCaypOqaYCAZ8yUG7Y5UhhF5w3KY5xie59gd ifu3PHdng59sD4RsYiQP8yZHtpDO5WgFLAm0miKq387kZvZbP/AJ X-Google-Smtp-Source: AGHT+IFHkeyNWpybeq4a22FDxFp6UqZiwsIeqK9MG7n2w8VMSaVh1OkCVzjissadAlByTDJzMhSjTA== X-Received: by 2002:a05:6a20:7aaf:b0:1a1:2ff0:4e2f with SMTP id u47-20020a056a207aaf00b001a12ff04e2fmr2553411pzh.60.1709334563529; Fri, 01 Mar 2024 15:09:23 -0800 (PST) Received: from localhost.localdomain ([2407:7000:8942:5500:c1d2:28d4:fa3c:e071]) by smtp.gmail.com with ESMTPSA id c11-20020aa781cb000000b006e4362d0d8csm3487509pfn.36.2024.03.01.15.09.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 Mar 2024 15:09:23 -0800 (PST) From: Barry Song <21cnbao@gmail.com> To: viro@zeniv.linux.org.uk, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Cc: herbert@gondor.apana.org.au, Barry Song Subject: [PATCH] iov_iter: call kmap on each page even for lowmem if CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP is enabled Date: Sat, 2 Mar 2024 12:09:08 +1300 Message-Id: <20240301230908.7507-1-21cnbao@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Barry Song copy_page_from_iter_atomic() has the assumption lowmem will only need one kmap to get start page_address() for all pages. This is wrong if the debug option CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP is enabled. This patch fixes it in the same way with skbuff.h by always applying kmap one by one even for lowmem, static inline bool skb_frag_must_loop(struct page *p) { #if defined(CONFIG_HIGHMEM) if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) || PageHighMem(p)) return true; #endif return false; } Reported-by: Herbert Xu Closes: https://lore.kernel.org/all/ZeGtrvm9WGv5cxQV@gondor.apana.org.au/ Signed-off-by: Barry Song --- -v1: Herbert found and pointed out this problem when he reviewed my patch in crypto/scompress.c; 99.9% of the credit for this patch goes to Herbert. lib/iov_iter.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index e0aa6b440ca5..2e8a5b32f152 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -490,7 +490,7 @@ size_t copy_page_from_iter_atomic(struct page *page, si= ze_t offset, char *p; =20 n =3D bytes - copied; - if (PageHighMem(page)) { + if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) || PageHighMem(page)) { page +=3D offset / PAGE_SIZE; offset %=3D PAGE_SIZE; n =3D min_t(size_t, n, PAGE_SIZE - offset); @@ -501,7 +501,8 @@ size_t copy_page_from_iter_atomic(struct page *page, si= ze_t offset, kunmap_atomic(p); copied +=3D n; offset +=3D n; - } while (PageHighMem(page) && copied !=3D bytes && n > 0); + } while ((IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) || PageHighMem(pa= ge)) + && copied !=3D bytes && n > 0); =20 return copied; } --=20 2.34.1