This is a note to let you know that I've just added the patch titled
nvmem: core: fix registration vs use race
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nvmem-core-fix-registration-vs-use-race.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ab3428cfd9aa2f3463ee4b2909b5bb2193bd0c4a Mon Sep 17 00:00:00 2001
From: "Russell King (Oracle)" <rmk+kernel@xxxxxxxxxxxxxxx>
Date: Fri, 27 Jan 2023 10:40:11 +0000
Subject: nvmem: core: fix registration vs use race
From: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
commit ab3428cfd9aa2f3463ee4b2909b5bb2193bd0c4a upstream.
The i.MX6 CPU frequency driver sometimes fails to register at boot time
due to nvmem_cell_read_u32() sporadically returning -ENOENT.
This happens because there is a window where __nvmem_device_get() in
of_nvmem_cell_get() is able to return the nvmem device, but as cells
have been setup, nvmem_find_cell_entry_by_node() returns NULL.
The occurs because the nvmem core registration code violates one of the
fundamental principles of kernel programming: do not publish data
structures before their setup is complete.
Fix this by making nvmem core code conform with this principle.
Fixes: eace75cfdcf7 ("nvmem: Add a simple NVMEM framework for nvmem providers")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230127104015.23839-7-srinivas.kandagatla@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/nvmem/core.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -832,22 +832,16 @@ struct nvmem_device *nvmem_register(cons
nvmem->dev.groups = nvmem_dev_groups;
#endif
- dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
-
- rval = device_add(&nvmem->dev);
- if (rval)
- goto err_put_device;
-
if (nvmem->nkeepout) {
rval = nvmem_validate_keepouts(nvmem);
if (rval)
- goto err_device_del;
+ goto err_put_device;
}
if (config->compat) {
rval = nvmem_sysfs_setup_compat(nvmem, config);
if (rval)
- goto err_device_del;
+ goto err_put_device;
}
if (config->cells) {
@@ -864,6 +858,12 @@ struct nvmem_device *nvmem_register(cons
if (rval)
goto err_remove_cells;
+ dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
+
+ rval = device_add(&nvmem->dev);
+ if (rval)
+ goto err_remove_cells;
+
blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem);
return nvmem;
@@ -873,8 +873,6 @@ err_remove_cells:
err_teardown_compat:
if (config->compat)
nvmem_sysfs_remove_compat(nvmem, config);
-err_device_del:
- device_del(&nvmem->dev);
err_put_device:
put_device(&nvmem->dev);
Patches currently in stable-queue which might be from rmk+kernel@xxxxxxxxxxxxxxx are
queue-6.1/nvmem-core-fix-registration-vs-use-race.patch
queue-6.1/nvmem-core-remove-nvmem_config-wp_gpio.patch
queue-6.1/nvmem-core-fix-return-value.patch
queue-6.1/nvmem-core-initialise-nvmem-id-early.patch
queue-6.1/nvmem-core-fix-cleanup-after-dev_set_name.patch
