From: Guenter Roeck Date: Mon, 27 Jul 2026 16:54:23 +0000 (-0700) Subject: hwmon: (nzxt-smart2) DMA-align output buffer X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=080bbf42faf77e6489ab30d5114c5f8f6ccbb1b8;p=thirdparty%2Flinux.git hwmon: (nzxt-smart2) DMA-align output buffer Sashiko reports: When send_output_report() calls hid_hw_output_report(), the underlying USB HID core calls usb_interrupt_msg() which maps this buffer directly for DMA. When the DMA mapping flushes or invalidates the cacheline, it will corrupt the adjacent variables (mutex, update_interval) that were modified concurrently by the CPU. This causes memory corruption due to cacheline sharing on non-coherent CPU architectures (such as ARM or MIPS). The DMA API debugging tool (CONFIG_DMA_API_DEBUG) will trigger runtime warnings for this violation. Any operation that triggers send_output_report() (like setting a fan speed or updating the interval) causes the USB DMA mapping. On systems with non-coherent caches, this structural bug causes immediate and deterministic memory corruption. Align the output buffer to ARCH_DMA_MINALIGN to fix the problem. Reported-by: Sashiko Fixes: 53e68c20aeb1 ("hwmon: add driver for NZXT RGB&Fan Controller/Smart Device v2.") Cc: Aleksandr Mezin Signed-off-by: Guenter Roeck --- diff --git a/drivers/hwmon/nzxt-smart2.c b/drivers/hwmon/nzxt-smart2.c index e2316c46629d..ff0c0bee0e83 100644 --- a/drivers/hwmon/nzxt-smart2.c +++ b/drivers/hwmon/nzxt-smart2.c @@ -203,7 +203,7 @@ struct drvdata { */ struct mutex mutex; long update_interval; - u8 output_buffer[OUTPUT_REPORT_SIZE]; + u8 output_buffer[OUTPUT_REPORT_SIZE] __aligned(ARCH_DMA_MINALIGN); }; static long scale_pwm_value(long val, long orig_max, long new_max)