FAILED: patch "[PATCH] hwmon: (pmbus/adm1266) serialize NVMEM blackbox read with" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 9f1dd8f9491eb840cbea7ffdf4cad031e25f8ae0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026052847-broadcast-elevating-8bc4@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9f1dd8f9491eb840cbea7ffdf4cad031e25f8ae0 Mon Sep 17 00:00:00 2001
From: Abdurrahman Hussain <[email protected]>
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.

index 0eef58dd69a6..5ddca5701032 100644
@@ -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);
 

From: Abdurrahman Hussain <[email protected]>

[ Upstream commit 9f1dd8f9491eb840cbea7ffdf4cad031e25f8ae0 ]

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.

---
 drivers/hwmon/pmbus/adm1266.c | 7 +++++++
 1 file changed, 7 insertions(+)

index a616439cecbf51..e265bfd93dd7c4 100644
@@ -395,18 +395,25 @@ static int adm1266_nvmem_read(void *priv, unsigned int offset, void *val, size_t
 	if (offset + bytes > data->nvmem_config.size)
 		return -EINVAL;
 
+	ret = pmbus_lock_interruptible(data->client);
+	if (ret)
+		return ret;
+
 	if (offset == 0) {
 		memset(data->dev_mem, 0, data->nvmem_config.size);
 
 		ret = adm1266_nvmem_read_blackbox(data, data->dev_mem);
 		if (ret) {
 			dev_err(&data->client->dev, "Could not read blackbox!");
+			pmbus_unlock(data->client);
 			return ret;
 		}
 	}
 
 	memcpy(val, data->dev_mem + offset, bytes);
 
+	pmbus_unlock(data->client);
+
 	return 0;
 }
 

2.53.0