From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 967B331ED7C; Thu, 16 Jul 2026 14:00:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210451; cv=none; b=XodYPOfrlt6Qv/K0whs2Mr/Y1cpl3tBZ3O5nPUk7bWM1J7pGtp3ek6DB83YK2eEvzdkxKXj5rG0eefa4w6inwJyAAmGLUH2/y3ErSCzTY//84bh5/YT/GMBECwhh3fFACgdHJRw8u0tF2VanRMNF3aVe7/OHlQX8+eSKTkD7cUQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210451; c=relaxed/simple; bh=z5Mm23v4+dX4TL7WmT7c9FGJKmtrKmm13820qBf79E8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=q1mKrTG/NJ+feBZ5g4bpIwpO7tJVLQW2o+m+rotT/+azCTGbY9RIbP0hyCBjzWakzTPBHNx/ElWm1oC5d2WGmrz3GBcZe5tbm8qEYrBZiHUAAeaz76xBddxoC5p6kRDmQFegX+7ZeGwbHHkQpuR79BSRXj5wdKx7mWaxIHa1CZ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Bro5T4k7; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Bro5T4k7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 069231F000E9; Thu, 16 Jul 2026 14:00:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784210450; bh=DO1wSSSuCKnDPzeNBYiTJgQcwmVUMBTMnOjfwstETQI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Bro5T4k7+xejVQxFUbZO1lgExpvNL8xXUD9017Vnd9QEQHVz9NZrln9tdc4WxBhIj 1OgM92J+y0TraTwzJj19oZ4QhB9tdqX4FJwTleyCmjugjXZS2CidAQF8yWTXvGFB8i HeMvm4LIHK3kjuh8O1KuifNng3h2841VTMp00gTc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Radu Sabau , Stable@vger.kernel.org, Jonathan Cameron Subject: [PATCH 6.18 053/480] iio: adc: ad_sigma_delta: fix clear_pending_event for registerless devices Date: Thu, 16 Jul 2026 15:26:40 +0200 Message-ID: <20260716133045.858436341@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133044.672218725@linuxfoundation.org> References: <20260716133044.672218725@linuxfoundation.org> User-Agent: quilt/0.69 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Radu Sabau commit 91bc6767a4f55dc470d8a56b55b9f2ea09094efe upstream. ad_sigma_delta_clear_pending_event() falls through to the status register read path for devices with has_registers = false and no rdy_gpiod. For such devices, ad_sd_read_reg() skips the address byte entirely and clocks raw MISO bytes with no address phase — making it byte-for-byte identical to reading conversion data. If a pending conversion result is present, this partially consumes it and corrupts the data stream for the subsequent ad_sd_read_reg() call in ad_sigma_delta_single_conversion(). Furthermore, with num_resetclks = 0 on these devices, data_read_len evaluates to 0. If the clocked byte has bit 7 clear, pending_event is set and the code attempts memset(data + 2, 0xff, 0 - 1), overflowing to SIZE_MAX and corrupting the heap. Fix by returning 0 immediately when neither rdy_gpiod nor has_registers is set. This is safe for all current registerless devices: ad7191 and ad7780 (with powerdown GPIO) are reset between conversions by CS deassertion, so there is no stale result to drain; ad7780 (without powerdown GPIO) and max11205 are continuously-converting and cycle ~DRDY at the output data rate regardless of whether the previous result was read, so the next falling edge fires naturally. A future registerless device that holds ~DRDY asserted until data is read would be broken by this early return and would require either num_resetclks set or a rdy-gpio. The same heap corruption is reachable on any device with rdy_gpiod set but num_resetclks = 0: if the GPIO indicates a pending event, the drain path executes memset(data + 2, 0xff, 0 - 1) regardless of has_registers. Add an explicit data_read_len == 0 guard after the pending event check; the stale result is then consumed by the first ad_sd_read_reg() call in ad_sigma_delta_single_conversion(). Fixes: 132d44dc6966 ("iio: adc: ad_sigma_delta: Check for previous ready signals") Signed-off-by: Radu Sabau Cc: Signed-off-by: Jonathan Cameron Signed-off-by: Greg Kroah-Hartman --- drivers/iio/adc/ad_sigma_delta.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) --- a/drivers/iio/adc/ad_sigma_delta.c +++ b/drivers/iio/adc/ad_sigma_delta.c @@ -260,11 +260,25 @@ static int ad_sigma_delta_clear_pending_ /* * Read R̅D̅Y̅ pin (if possible) or status register to check if there is an - * old event. + * old event. For devices with neither an RDY GPIO nor registers, + * ad_sd_read_reg() transmits no address byte and clocks raw MISO bytes, + * which is indistinguishable from reading conversion data and would + * partially consume a pending result. Skip the check for such devices. + * + * This is safe for all current registerless devices: ad7191 and ad7780 + * (with powerdown GPIO) are reset between conversions by CS deassertion, + * so there is no stale result to drain; ad7780 (without powerdown GPIO) + * and max11205 are continuously-converting and cycle ~DRDY at the output + * data rate regardless of whether the previous result was read, so the + * next falling edge fires naturally. + * + * A future registerless device that holds ~DRDY asserted until data is + * read would be broken by this early return and would need either + * num_resetclks set or a rdy-gpio. */ if (sigma_delta->rdy_gpiod) { pending_event = gpiod_get_value(sigma_delta->rdy_gpiod); - } else { + } else if (sigma_delta->info->has_registers) { unsigned int status_reg; ret = ad_sd_read_reg(sigma_delta, AD_SD_REG_STATUS, 1, &status_reg); @@ -272,12 +286,25 @@ static int ad_sigma_delta_clear_pending_ return ret; pending_event = !(status_reg & AD_SD_REG_STATUS_RDY); + } else { + return 0; } if (!pending_event) return 0; /* + * With num_resetclks = 0, data_read_len is 0 and the drain sequence + * below would compute memset(data + 2, 0xff, 0 - 1), underflowing to + * SIZE_MAX and corrupting the heap. There is no safe way to drain the + * stale result without knowing the data register size; it will be + * consumed by the first ad_sd_read_reg() call in + * ad_sigma_delta_single_conversion(). + */ + if (!data_read_len) + return 0; + + /* * In general the size of the data register is unknown. It varies from * device to device, might be one byte longer if CONTROL.DATA_STATUS is * set and even varies on some devices depending on which input is