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 43C5F2584 for ; Thu, 23 Feb 2023 13:11:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE8BCC433D2; Thu, 23 Feb 2023 13:11:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1677157883; bh=60ZF3qwHgY5n8GYM8lY2Wr1z1mMvQ8sc5JEY6YBajKo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GEN/RpPmsGtzCNxlECUvfWX6R39YHgTFxw2JqD/tnPWhc8zTinGfirEp8HQ9stc6/ +geLfZRSkTBLdoP/Wmozm/RjqpS5/CsJBOwOBYmjxLbjeOgAuiMrtBxB1KTdtBJSs9 gs0PrhZ5JXA8+Rn3xFpYKp2NBrxwDX+9qmZgRwf0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dominik Brodowski , PaX Team , Emese Revfy , "Jason A. Donenfeld" , Sasha Levin Subject: [PATCH 5.15 10/36] random: always mix cycle counter in add_latent_entropy() Date: Thu, 23 Feb 2023 14:06:46 +0100 Message-Id: <20230223130429.548342879@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230223130429.072633724@linuxfoundation.org> References: <20230223130429.072633724@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Jason A. Donenfeld [ Upstream commit d7bf7f3b813e3755226bcb5114ad2ac477514ebf ] add_latent_entropy() is called every time a process forks, in kernel_clone(). This in turn calls add_device_randomness() using the latent entropy global state. add_device_randomness() does two things: 2) Mixes into the input pool the latent entropy argument passed; and 1) Mixes in a cycle counter, a sort of measurement of when the event took place, the high precision bits of which are presumably difficult to predict. (2) is impossible without CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y. But (1) is always possible. However, currently CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n disables both (1) and (2), instead of just (2). This commit causes the CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n case to still do (1) by passing NULL (len 0) to add_device_randomness() when add_latent_ entropy() is called. Cc: Dominik Brodowski Cc: PaX Team Cc: Emese Revfy Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin") Signed-off-by: Jason A. Donenfeld Signed-off-by: Sasha Levin --- include/linux/random.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/random.h b/include/linux/random.h index 3feafab498ad9..ed75fb2b0ca94 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -19,14 +19,14 @@ void add_input_randomness(unsigned int type, unsigned int code, void add_interrupt_randomness(int irq) __latent_entropy; void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy); -#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__) static inline void add_latent_entropy(void) { +#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__) add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); -} #else -static inline void add_latent_entropy(void) { } + add_device_randomness(NULL, 0); #endif +} void get_random_bytes(void *buf, size_t len); size_t __must_check get_random_bytes_arch(void *buf, size_t len); -- 2.39.0