From 9f1dd8f9491eb840cbea7ffdf4cad031e25f8ae0 Mon Sep 17 00:00:00 2001 From: Abdurrahman Hussain Date: Mon, 18 May 2026 17:52:31 -0700 Subject: [PATCH] hwmon: (pmbus/adm1266) serialize NVMEM blackbox read with pmbus_lock adm1266_nvmem_read() is the reg_read callback the NVMEM core invokes when userspace reads /sys/bus/nvmem/devices/.../nvmem on this chip. On the first byte of every read it does a memset of data->dev_mem, walks the device blackbox through adm1266_nvmem_read_blackbox() (which issues a chain of PMBus block transactions), and then memcpys the refreshed buffer out to userspace. None of that runs under pmbus_lock today. Two consequences: - The PMBus traffic the refresh issues is not serialised against pmbus_core's own multi-step PAGE+register sequences. A paged hwmon attribute read from another thread can land between a PAGE write and the paged read in either direction and corrupt one side's view of the device state machine. - The NVMEM core does not serialise concurrent reg_read calls, so two userspace readers racing at offset 0 can interleave the memset of data->dev_mem with another reader's adm1266_nvmem_read_blackbox() refill or memcpy out, returning torn data to userspace. Take pmbus_lock at the top of adm1266_nvmem_read() via the scope-based guard(). Patch 5 of this series moves adm1266_config_nvmem() past pmbus_do_probe() so the lock is guaranteed to be live before the callback is reachable from userspace. Fixes: 15609d189302 ("hwmon: (pmbus/adm1266) read blackbox") Cc: stable@vger.kernel.org Signed-off-by: Abdurrahman Hussain Link: https://lore.kernel.org/r/20260518-adm1266-gpio-fixes-v3-7-e425e4f88139@nexthop.ai Signed-off-by: Guenter Roeck --- drivers/hwmon/pmbus/adm1266.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/hwmon/pmbus/adm1266.c b/drivers/hwmon/pmbus/adm1266.c index 0eef58dd69a6..5ddca5701032 100644 --- a/drivers/hwmon/pmbus/adm1266.c +++ b/drivers/hwmon/pmbus/adm1266.c @@ -400,6 +400,8 @@ static int adm1266_nvmem_read(void *priv, unsigned int offset, void *val, size_t if (offset + bytes > data->nvmem_config.size) return -EINVAL; + guard(pmbus_lock)(data->client); + if (offset == 0) { memset(data->dev_mem, 0, data->nvmem_config.size);