From 26d5ff79768548efb1e604bb6e8697c101e06269 Mon Sep 17 00:00:00 2001 From: Yibo Tan Date: Fri, 11 Sep 2026 15:18:09 +0800 Subject: [PATCH] hwmon: (pwm-fan) Stop RPM timer before freeing tach data sample_timer() rearms the RPM timer and accesses the devm-managed ctx->tachs and ctx->pulses_per_revolution arrays. The cleanup action which stops the timer is registered before those arrays are allocated. Since devres releases entries in reverse order, driver detach can free the arrays before pwm_fan_cleanup() shuts down the timer. A timer expiry in that window accesses the freed tach data. With a KASAN kernel, a test-only kprobe delayed entry to pwm_fan_cleanup() while normal sysfs unbind ran. Each of three runs reported three four-byte reads and two four-byte writes in sample_timer() after its backing devm allocations had been freed. The helper did not invoke the timer callback, cleanup actions or free functions. With the fix, three matching unbind runs completed without KASAN, BUG, WARNING, Oops or panic. Instrumentation confirmed that timer retirement completed before the first timer backing allocation was released. Split timer retirement from the power cleanup and register its devres action after the timer backing data and IRQ actions are installed. This preserves the early power rollback action while ensuring the timer is retired before its backing data is released. Use timer_shutdown_sync() because the callback can rearm itself. Fixes: 01695410d452 ("hwmon: (pwm-fan) Store tach data separately") Cc: stable@vger.kernel.org Assisted-by: Codex:GPT-5 Signed-off-by: Yibo Tan Link: https://patch.msgid.link/20260911071809.130151-1-lhfff@tju.edu.cn Signed-off-by: Guenter Roeck --- drivers/hwmon/pwm-fan.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c index 3b87f65bae05..c633d7f6464c 100644 --- a/drivers/hwmon/pwm-fan.c +++ b/drivers/hwmon/pwm-fan.c @@ -483,7 +483,6 @@ static void pwm_fan_cleanup(void *__ctx) { struct pwm_fan_ctx *ctx = __ctx; - timer_delete_sync(&ctx->rpm_timer); if (ctx->pwm_shutdown) { ctx->enable_mode = pwm_enable_reg_enable; __set_pwm(ctx, ctx->pwm_shutdown); @@ -494,6 +493,13 @@ static void pwm_fan_cleanup(void *__ctx) } } +static void pwm_fan_timer_cleanup(void *__ctx) +{ + struct pwm_fan_ctx *ctx = __ctx; + + timer_shutdown_sync(&ctx->rpm_timer); +} + static int pwm_fan_probe(struct platform_device *pdev) { struct thermal_cooling_device *cdev; @@ -644,6 +650,10 @@ static int pwm_fan_probe(struct platform_device *pdev) } if (ctx->tach_count > 0) { + ret = devm_add_action_or_reset(dev, pwm_fan_timer_cleanup, ctx); + if (ret) + return ret; + ctx->sample_start = ktime_get(); mod_timer(&ctx->rpm_timer, jiffies + HZ); @@ -700,6 +710,7 @@ static void pwm_fan_shutdown(struct platform_device *pdev) { struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev); + pwm_fan_timer_cleanup(ctx); pwm_fan_cleanup(ctx); }