linux-kernel - Re: [PATCH v4] staging: iio: adc: ad7816: fix race condition in SPI operations

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <51042a87-0233-4748-b3c0-b167d3a4fa06@baylibre.com>
Date: Mon, 1 Sep 2025 12:00:44 -0500
From: David Lechner <dlechner@...libre.com>
To: Mohammad Amin Hosseini <moahmmad.hosseinii@...il.com>,
 linux-iio@...r.kernel.org, linux-staging@...ts.linux.dev
Cc: linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
 jic23@...nel.org, lars@...afoo.de, Michael.Hennerich@...log.com,
 nuno.sa@...log.com, andy@...nel.org, sonic.zhang@...log.com,
 vapier@...too.org, dan.carpenter@...aro.org
Subject: Re: [PATCH v4] staging: iio: adc: ad7816: fix race condition in SPI
 operations

On 9/1/25 11:03 AM, Mohammad Amin Hosseini wrote:
> The ad7816 driver lacks proper synchronization around SPI operations
> and device state access. Concurrent access from multiple threads can
> lead to data corruption and inconsistent device state.
> 
> The driver performs sequences of GPIO pin manipulations followed by
> SPI transactions without any locking. Device state variables (mode,
> channel_id, oti_data) are also accessed without synchronization.
> 
> This bug was found through manual code review using static analysis
> techniques. The review focused on identifying unsynchronized access
> patterns to shared resources. Key indicators were:
> - GPIO pin state changes followed by SPI operations without atomicity
> - Shared state variables accessed from multiple sysfs entry points
> - No mutex or spinlock protection around sections
> - Potential for interleaved execution in multi-threaded environments
> 
> The review methodology involved tracing data flow paths and identifying
> points where concurrent access could corrupt device state or SPI
> communication sequences.
> 
> Add io_lock mutex to protect:
> - SPI transactions and GPIO sequences in read/write functions
> - Device state variables in sysfs show/store functions
> - Concurrent access to chip configuration
> 
> This prevents race conditions when multiple processes access the device
> simultaneously through sysfs attributes or device file operations.
> 
> Fixes: 7924425db04a ("staging: iio: adc: new driver for AD7816 devices")
> 
> Signed-off-by: Mohammad Amin Hosseini <moahmmad.hosseinii@...il.com>
> 
> ---
> Changes in v4:
> - Added locking to reader functions (show_mode, show_channel, show_oti)
> - Fixed incomplete reader/writer synchronization that could still race
> - Ensured all device state access is properly synchronized
> - Replace sprintf() with sysfs_emit() in all sysfs show functions
> - Use sysfs_streq() instead of strcmp() for proper input parsing
> - Implement locked/unlocked SPI function variants to prevent deadlock
> - Use channel snapshot to ensure atomic read operations
> - Fix sizeof() usage in spi_read to be more explicit (sizeof(buf))
> - Make oti write operations atomic (SPI write + shadow update under lock)
> - Fix race condition in ad7816_set_oti() by taking channel_id snapshot under lock
> - Fix return type consistency (ssize_t vs int) in show functions
> - Use chip->id instead of string comparison for channel validation
> - Add explicit cast for narrowing assignment
> - Add default case for unknown chip ID validation
> - Use cansleep GPIO variants in sleepable context
> - Improve lock documentation for protected resources
> ---

This is way to much to do in a single patch. Also, given that this
part is obsolete [1] and this driver is in staging, is it really
worth all of this effort to fix it up?

[1]: https://www.analog.com/en/products/ad7816.html