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From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
To: gregkh@linuxfoundation.org
Cc: linux-kernel@vger.kernel.org,
	"Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>,
	stable@vger.kernel.org,
	Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Subject: [PATCH 06/10] nvmem: core: fix registration vs use race
Date: Fri, 27 Jan 2023 10:40:11 +0000	[thread overview]
Message-ID: <20230127104015.23839-7-srinivas.kandagatla@linaro.org> (raw)
In-Reply-To: <20230127104015.23839-1-srinivas.kandagatla@linaro.org>

From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>

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fundamental principles of kernel programming: do not publish data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.

Cc: stable@vger.kernel.org
Fixes: eace75cfdcf7 ("nvmem: Add a simple NVMEM framework for nvmem providers")
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
 drivers/nvmem/core.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index ac77a019aed7..e92c6f1aadbb 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -832,22 +832,16 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 	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(const struct nvmem_config *config)
 	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 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 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);
 
-- 
2.25.1


  parent reply	other threads:[~2023-01-27 10:40 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-27 10:40 [PATCH 00/10] nvmem: fixes for 6.2 Srinivas Kandagatla
2023-01-27 10:40 ` [PATCH 01/10] nvmem: brcm_nvram: Add check for kzalloc Srinivas Kandagatla
2023-01-27 10:40 ` [PATCH 02/10] nvmem: sunxi_sid: Always use 32-bit MMIO reads Srinivas Kandagatla
2023-01-27 10:40 ` [PATCH 03/10] nvmem: core: initialise nvmem->id early Srinivas Kandagatla
2023-01-27 10:40 ` [PATCH 04/10] nvmem: core: remove nvmem_config wp_gpio Srinivas Kandagatla
2023-01-27 10:40 ` [PATCH 05/10] nvmem: core: fix cleanup after dev_set_name() Srinivas Kandagatla
2023-01-27 10:40 ` Srinivas Kandagatla [this message]
2023-01-27 10:40 ` [PATCH 07/10] nvmem: core: fix device node refcounting Srinivas Kandagatla
2023-01-27 10:40 ` [PATCH 08/10] nvmem: core: fix cell removal on error Srinivas Kandagatla
2023-01-27 10:40 ` [PATCH 09/10] nvmem: core: fix return value Srinivas Kandagatla
2023-01-27 10:40 ` [PATCH 10/10] nvmem: qcom-spmi-sdam: fix module autoloading Srinivas Kandagatla
2023-01-28 13:39 ` [PATCH 00/10] nvmem: fixes for 6.2 Greg KH
2023-01-30 11:03   ` Srinivas Kandagatla

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