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 9DFCA26FD83; Tue, 8 Apr 2025 12:49:32 +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=1744116572; cv=none; b=l3h6SLXYgV+gG7jkPY4goYPsFhVL74KzxyWPFjT2k69xxxVWVT68H+NCQiqWmTiJNLHZVj1PH7SYgK4g2/nGAYf1CLfxqLqVcdK1f5KjOpU1WZ22w2qK82gGLCIMo2Qx9NOCSAjq2vbxT79r945UE6vLdFNjK8uJO4P/963Mwic= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744116572; c=relaxed/simple; bh=Bm+BLw0bjvEb0D7exc5H9yBEH7Pc7GYjn8XrmGtfnag=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=u7ALtJpsQAfBYoXW9rjtflk4lubPZ5TV1uSzbYveJaLmqQoxMiupqWVJTpTwY+NOnoQZ7x84zOsbWjT/ScWb4hjlfe9MCgFgyJLrGhas4Xn+3yZhw79GH+MEPPOsfgzcuo9YLwfoe/DPwXqZcFfPeqUTU5NqVTWgY+YnEb4a2cg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=k4dzVHz2; 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="k4dzVHz2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FB42C4CEE5; Tue, 8 Apr 2025 12:49:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744116572; bh=Bm+BLw0bjvEb0D7exc5H9yBEH7Pc7GYjn8XrmGtfnag=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k4dzVHz2E3xT+ZNXQmVxwies9UQzFwvqWH4m1VsJmPQp7yzYKf6hfVXslq7V514go WiXdaXBszZSS7Jbk1OObM6r7UQkutrSW34pxJpjs5cStcCqr9j4JMJDdpTf6H3Y49C in8I2rpyNzNZyjnKfzCINbSfHYb6RZ1jVhysH8oo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Jonathan Cameron , Sasha Levin Subject: [PATCH 6.12 190/423] iio: adc: ad7173: Fix comparison of channel configs Date: Tue, 8 Apr 2025 12:48:36 +0200 Message-ID: <20250408104850.163860834@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104845.675475678@linuxfoundation.org> References: <20250408104845.675475678@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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Uwe Kleine-König [ Upstream commit 7b6033ed5a9e1a369a9cf58018388ae4c5f17e41 ] Checking the binary representation of two structs (of the same type) for equality doesn't have the same semantic as comparing all members for equality. The former might find a difference where the latter doesn't in the presence of padding or when ambiguous types like float or bool are involved. (Floats typically have different representations for single values, like -0.0 vs +0.0, or 0.5 * 2² vs 0.25 * 2³. The type bool has at least 8 bits and the raw values 1 and 2 (probably) both evaluate to true, but memcmp finds a difference.) When searching for a channel that already has the configuration we need, the comparison by member is the one that is needed. Convert the comparison accordingly to compare the members one after another. Also add a static_assert guard to (somewhat) ensure that when struct ad7173_channel_config::config_props is expanded, the comparison is adapted, too. This issue is somewhat theoretic, but using memcmp() on a struct is a bad pattern that is worth fixing. Fixes: 76a1e6a42802 ("iio: adc: ad7173: add AD7173 driver") Signed-off-by: Uwe Kleine-König Link: https://patch.msgid.link/20250303114659.1672695-14-u.kleine-koenig@baylibre.com Signed-off-by: Jonathan Cameron Signed-off-by: Sasha Levin --- drivers/iio/adc/ad7173.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c index 5a65be00dd190..2eebc6f761a63 100644 --- a/drivers/iio/adc/ad7173.c +++ b/drivers/iio/adc/ad7173.c @@ -181,7 +181,11 @@ struct ad7173_channel_config { u8 cfg_slot; bool live; - /* Following fields are used to compare equality. */ + /* + * Following fields are used to compare equality. If you + * make adaptations in it, you most likely also have to adapt + * ad7173_find_live_config(), too. + */ struct_group(config_props, bool bipolar; bool input_buf; @@ -582,15 +586,28 @@ static struct ad7173_channel_config * ad7173_find_live_config(struct ad7173_state *st, struct ad7173_channel_config *cfg) { struct ad7173_channel_config *cfg_aux; - ptrdiff_t cmp_size; int i; - cmp_size = sizeof_field(struct ad7173_channel_config, config_props); + /* + * This is just to make sure that the comparison is adapted after + * struct ad7173_channel_config was changed. + */ + static_assert(sizeof_field(struct ad7173_channel_config, config_props) == + sizeof(struct { + bool bipolar; + bool input_buf; + u8 odr; + u8 ref_sel; + })); + for (i = 0; i < st->num_channels; i++) { cfg_aux = &st->channels[i].cfg; if (cfg_aux->live && - !memcmp(&cfg->config_props, &cfg_aux->config_props, cmp_size)) + cfg->bipolar == cfg_aux->bipolar && + cfg->input_buf == cfg_aux->input_buf && + cfg->odr == cfg_aux->odr && + cfg->ref_sel == cfg_aux->ref_sel) return cfg_aux; } return NULL; -- 2.39.5