[PATCH net v2] devlink: request flash firmware without instance lock

[Miguel Garcia <miguelgarciaroman8@gmail.com>]

request_firmware() may enter the userspace fallback and call
try_to_freeze(). Holding the devlink instance lock across that call
triggers a lockdep warning and can block unregister for the duration of
the firmware fallback.

Drop the instance lock around firmware loading in both flash update paths.
The callers hold a devlink reference, which also pins the parent device.
Recheck registration after reacquiring the lock before calling into the
driver.

Fixes: b44cfd4f5b91 ("devlink: move request_firmware out of driver")
Reported-by: syzbot+372a7d84708b07f64d9b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=372a7d84708b07f64d9b
Signed-off-by: Miguel Garcia <miguelgarciaroman8@gmail.com>
---
Changes in v2:
- Cc Jacob Keller, author of b44cfd4f5b91, as requested by Andrew Lunn.
- Keep only b44cfd4f5b91 as the Fixes tag; ed539ba614a0 provides the
  registration check but did not introduce the locking bug.

v1: https://lore.kernel.org/r/20260829142525.3900565-1-miguelgarciaroman8@gmail.com

 net/devlink/dev.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/net/devlink/dev.c b/net/devlink/dev.c
index 55959b0ff..cdbf39f19 100644
--- a/net/devlink/dev.c
+++ b/net/devlink/dev.c
@@ -1169,17 +1169,25 @@ int devlink_nl_flash_update_doit(struct sk_buff *skb, struct genl_info *info)
 
 	nla_file_name = info->attrs[DEVLINK_ATTR_FLASH_UPDATE_FILE_NAME];
 	file_name = nla_data(nla_file_name);
+	devl_unlock(devlink);
 	ret = request_firmware(&params.fw, file_name, devlink->dev);
+	devl_lock(devlink);
 	if (ret) {
 		NL_SET_ERR_MSG_ATTR(info->extack, nla_file_name,
 				    "failed to locate the requested firmware file");
 		return ret;
 	}
+	/* The device may have been unregistered while the lock was dropped. */
+	if (!devl_is_registered(devlink)) {
+		ret = -ENODEV;
+		goto out_release;
+	}
 
 	devlink_flash_update_begin_notify(devlink);
 	ret = devlink->ops->flash_update(devlink, &params, info->extack);
 	devlink_flash_update_end_notify(devlink);
 
+out_release:
 	release_firmware(params.fw);
 
 	return ret;
@@ -1244,15 +1252,24 @@ int devlink_compat_flash_update(struct devlink *devlink, const char *file_name)
 		ret = -EOPNOTSUPP;
 		goto out_unlock;
 	}
+	devl_unlock(devlink);
 
 	ret = request_firmware(&params.fw, file_name, devlink->dev);
+	devl_lock(devlink);
 	if (ret)
 		goto out_unlock;
 
+	/* The device may have been unregistered while the lock was dropped. */
+	if (!devl_is_registered(devlink)) {
+		ret = -ENODEV;
+		goto out_release;
+	}
+
 	devlink_flash_update_begin_notify(devlink);
 	ret = devlink->ops->flash_update(devlink, &params, NULL);
 	devlink_flash_update_end_notify(devlink);
 
+out_release:
 	release_firmware(params.fw);
 out_unlock:
 	devl_unlock(devlink);
-- 
2.43.0