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 A213D2E7649; Thu, 3 Jul 2025 15:02:11 +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=1751554931; cv=none; b=LXp0jEGWl3U0FhfbIU1YmA/cVSSkldiKxfert1TEp7OvOqvbnEUEFBqwMm6VVDt4R/ykRIQ6WsY9FcIisksmuAUBahuUK2jxgy7kDSywblchyByufQPC+7Oru5KS5DHL009Hb+eBgXSvi9TRdzQXk9G6s2m2xn/CXddhjMmu770= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751554931; c=relaxed/simple; bh=Jf6n4+AZO3mYERWxWmsMPrSzOtXwx+ODykdWPOjLP9I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ApzDytJNdxU1YH7b/6047ipSIZre3MXe2ZOgsTvDHV2cz58f/yhCmnkrCtYn4ZkjlMzf3/ukj2H6dHJtmE3cw0Z0QKapxpB05FeurAZ8qGlsCbtarT+38Y4y4NFVstEuxvAyF8E/ch+KXKhxf9fZriEXGktlA44tBV3yyNpDnHE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=AxE30ZpI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="AxE30ZpI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C02D6C4CEEE; Thu, 3 Jul 2025 15:02:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1751554931; bh=Jf6n4+AZO3mYERWxWmsMPrSzOtXwx+ODykdWPOjLP9I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AxE30ZpIV3Gd2sbZ3a/p3km2Oy+PHseXPM9BFmLdtQ8xgQdcFpOkoFt00ccJaLmGZ +AyJaMxPnFIcRoRsqlRIbFMIaLvmF3H6hn1n3aS3GO8YG7nVrzWtStXfiosA0xqH9K gF8zY5K7QbQ+RIxNDb38mk3abXsQ7XTXxgjGeFyU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, rtm@csail.mit.edu, Nam Cao , Alexandre Ghiti , Palmer Dabbelt Subject: [PATCH 6.15 122/263] Revert "riscv: Define TASK_SIZE_MAX for __access_ok()" Date: Thu, 3 Jul 2025 16:40:42 +0200 Message-ID: <20250703144009.245056181@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250703144004.276210867@linuxfoundation.org> References: <20250703144004.276210867@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nam Cao commit 890ba5be6335dbbbc99af14ea007befb5f83f174 upstream. This reverts commit ad5643cf2f69 ("riscv: Define TASK_SIZE_MAX for __access_ok()"). This commit changes TASK_SIZE_MAX to be LONG_MAX to optimize access_ok(), because the previous TASK_SIZE_MAX (default to TASK_SIZE) requires some computation. The reasoning was that all user addresses are less than LONG_MAX, and all kernel addresses are greater than LONG_MAX. Therefore access_ok() can filter kernel addresses. Addresses between TASK_SIZE and LONG_MAX are not valid user addresses, but access_ok() let them pass. That was thought to be okay, because they are not valid addresses at hardware level. Unfortunately, one case is missed: get_user_pages_fast() happily accepts addresses between TASK_SIZE and LONG_MAX. futex(), for instance, uses get_user_pages_fast(). This causes the problem reported by Robert [1]. Therefore, revert this commit. TASK_SIZE_MAX is changed to the default: TASK_SIZE. This unfortunately reduces performance, because TASK_SIZE is more expensive to compute compared to LONG_MAX. But correctness first, we can think about optimization later, if required. Reported-by: Closes: https://lore.kernel.org/linux-riscv/77605.1750245028@localhost/ Signed-off-by: Nam Cao Cc: stable@vger.kernel.org Reviewed-by: Alexandre Ghiti Fixes: ad5643cf2f69 ("riscv: Define TASK_SIZE_MAX for __access_ok()") Link: https://lore.kernel.org/r/20250619155858.1249789-1-namcao@linutronix.de Signed-off-by: Palmer Dabbelt Signed-off-by: Greg Kroah-Hartman --- arch/riscv/include/asm/pgtable.h | 1 - 1 file changed, 1 deletion(-) --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -980,7 +980,6 @@ static inline pte_t pte_swp_clear_exclus */ #ifdef CONFIG_64BIT #define TASK_SIZE_64 (PGDIR_SIZE * PTRS_PER_PGD / 2) -#define TASK_SIZE_MAX LONG_MAX #ifdef CONFIG_COMPAT #define TASK_SIZE_32 (_AC(0x80000000, UL) - PAGE_SIZE)