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 014E7247291 for ; Sun, 14 Jun 2026 05:59:35 +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=1781416777; cv=none; b=tgGc7nxYMqxiptN2Xd3uR1gLvW6TXVkWe3Y/tIHSVFl09S0wFutvLk4JMfHB9hcfyAKVZjHJ85Do+nsocN6LDPQaSPFjdSIoOSDbQlNI6fl2IiZCRvg8byAcweY0DJitthV5z+GGMYJbnROleMS/hz+jU8xup94zdEiaNRUXfOQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781416777; c=relaxed/simple; bh=+FIKRxBw6lN0AQG6DUBMYUV54i6EbfD2UiwY43krGe8=; h=Subject:To:From:Date:Message-ID:MIME-Version:Content-Type; b=GryZPQkOLUnvpt1V9euuDy2VV7GSBd706qH54KBEQeCUNm7cokWkUe7ItYKE/oNt7n2iqc2Zv99PbsxSkAUrautUKsxPOY0a00RVKkgapfnkloQibVWEn7BTbEFJGG9BuC4mOJy704pP2LDMnP0d+N/1CfyZv1NQYsXDIFArZBE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kli91Gz/; 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="kli91Gz/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0615D1F000E9; Sun, 14 Jun 2026 05:59:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781416775; bh=UNvQMebKjyDQ4b5KbfDWxuA/BI6Kjm+VUSOjfrZ8Rp8=; h=Subject:To:From:Date; b=kli91Gz/GCfJZaVjgnRauVqPkf7M6SOoqxCgrtCocGMX6Mc8F0Ifc/0Mpw6IksGOB WJuD6dRRV6cooiv8WhfMZB2WUqMs7RRgfr/w/UXmwo+v+LHAOaV2YYnPMgT682zKjF ahGTQ5vEf2Q6+rijAtLKxT7t/7jXPYdTVe3eFz+Q= Subject: patch "iio: adc: ad_sigma_delta: fix clear_pending_event for registerless" added to char-misc-testing To: radu.sabau@analog.com,Stable@vger.kernel.org,jic23@kernel.org From: Date: Sun, 14 Jun 2026 07:57:26 +0200 Message-ID: <2026061426-tweak-universal-be07@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is a note to let you know that I've just added the patch titled iio: adc: ad_sigma_delta: fix clear_pending_event for registerless to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-testing branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will be merged to the char-misc-next branch sometime soon, after it passes testing, and the merge window is open. If you have any questions about this process, please let me know. >From 91bc6767a4f55dc470d8a56b55b9f2ea09094efe Mon Sep 17 00:00:00 2001 From: Radu Sabau Date: Wed, 27 May 2026 12:38:39 +0300 Subject: iio: adc: ad_sigma_delta: fix clear_pending_event for registerless devices MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- drivers/iio/adc/ad_sigma_delta.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c index 651ade67ad2e..1b410291da53 100644 --- a/drivers/iio/adc/ad_sigma_delta.c +++ b/drivers/iio/adc/ad_sigma_delta.c @@ -262,11 +262,25 @@ static int ad_sigma_delta_clear_pending_event(struct ad_sigma_delta *sigma_delta /* * 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); @@ -274,11 +288,24 @@ static int ad_sigma_delta_clear_pending_event(struct ad_sigma_delta *sigma_delta 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 -- 2.54.0