From 2e9a7f68329be41792c0b123c28e6c53c2fa2249 Mon Sep 17 00:00:00 2001 From: Andy Shevchenko Date: Thu, 18 Jun 2026 16:49:34 +0200 Subject: [PATCH 1/2] i2c: mpc: Fix timeout calculations At first glance the harmless cleanup of the driver does nothing bad. However, as the operator precedence list states the '*' (multiplication) and '/' division operators have order 5 with left-to-right associativity the *= has order 17 and associativity right-to-left. It wouldn't be a problem to replace foo = foo * HZ / 1000000; with foo *= HZ / 1000000; if HZ constant is in Hertz. The problem is that in the Linux kernel HZ is defined in jiffy units, which is order of magnitude smaller than a million. That's why operator precedence has a crucial role here. Fix the regression by reverting pre-optimized calculations. Fixes: be40a3ae719f ("i2c: mpc: Use of_property_read_u32 instead of of_get_property") Signed-off-by: Andy Shevchenko Cc: # v6.4+ Reviewed-by: Chris Packham Signed-off-by: Andi Shyti Link: https://lore.kernel.org/r/20260618144934.3249950-1-andriy.shevchenko@linux.intel.com --- drivers/i2c/busses/i2c-mpc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c index 28c5c5c1fb7a..a21fa45bd64c 100644 --- a/drivers/i2c/busses/i2c-mpc.c +++ b/drivers/i2c/busses/i2c-mpc.c @@ -844,7 +844,7 @@ static int fsl_i2c_probe(struct platform_device *op) "fsl,timeout", &mpc_ops.timeout); if (!result) { - mpc_ops.timeout *= HZ / 1000000; + mpc_ops.timeout = mpc_ops.timeout * HZ / 1000000; if (mpc_ops.timeout < 5) mpc_ops.timeout = 5; } else { From 10dd1a736d557e310a77117832874729a0175d57 Mon Sep 17 00:00:00 2001 From: Mingyu Wang <25181214217@stu.xidian.edu.cn> Date: Tue, 12 May 2026 17:35:34 +0800 Subject: [PATCH 2/2] i2c: i801: fix hardware state machine corruption in error path A severe livelock and subsequent Hung Task panic were observed in the i2c-i801 driver during concurrent Fuzzing. The crash is caused by an unconditional hardware register cleanup in the error handling path of i801_access(). When i801_check_pre() fails (e.g., returning -EBUSY because the SMBus controller is actively used by BIOS/ACPI), the kernel does not actually acquire the hardware ownership. However, the code jumps to the 'out' label and executes: iowrite8(SMBHSTSTS_INUSE_STS | STATUS_FLAGS, SMBHSTSTS(priv)); This forcefully clears the INUSE_STS lock and resets the hardware status flags without owning the controller. Doing so interrupts ongoing BIOS/ACPI transactions and totally corrupts the SMBus hardware state machine. Consequently, all subsequent i801_access() calls fail at the pre-check stage, triggering an endless stream of "SMBus is busy, can't use it!" error logs. Over a slow serial console, this printk flood monopolizes the CPU (Console Livelock), starving other processes trying to acquire the mmap_lock down_read semaphore, ultimately triggering the hung task watchdog. Fix this by moving the 'out' label below the hardware register cleanup. If i801_check_pre() fails, we safely bypass the iowrite8() and only release the software locks (pm_runtime and mutex), strictly adhering to the rule of not releasing resources that were never acquired. Fixes: 1f760b87e54c ("i2c: i801: Call i801_check_pre() from i801_access()") Signed-off-by: Mingyu Wang <25181214217@stu.xidian.edu.cn> Cc: # v6.3+ Signed-off-by: Andi Shyti Link: https://lore.kernel.org/r/20260512093534.348655-1-w15303746062@163.com --- drivers/i2c/busses/i2c-i801.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c index 32a3cef02c7b..b29c99ed3883 100644 --- a/drivers/i2c/busses/i2c-i801.c +++ b/drivers/i2c/busses/i2c-i801.c @@ -931,13 +931,13 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr, */ if (hwpec) iowrite8(ioread8(SMBAUXCTL(priv)) & ~SMBAUXCTL_CRC, SMBAUXCTL(priv)); -out: /* * Unlock the SMBus device for use by BIOS/ACPI, * and clear status flags if not done already. */ iowrite8(SMBHSTSTS_INUSE_STS | STATUS_FLAGS, SMBHSTSTS(priv)); +out: pm_runtime_put_autosuspend(&priv->pci_dev->dev); mutex_unlock(&priv->acpi_lock); return ret;