linux-kernel - [PATCH] nvmem: core: limit cell sysfs permissions to main attribute ones

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Message-Id: <20240619-nvmem-cell-sysfs-perm-v1-1-e5b7882fdfa8@weissschuh.net>
Date: Wed, 19 Jun 2024 20:09:00 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Marco Felsch <m.felsch@...gutronix.de>, linux-kernel@...r.kernel.org, 
 stable@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH] nvmem: core: limit cell sysfs permissions to main
 attribute ones

The cell sysfs attribute should not provide more access to the nvmem
data than the main attribute itself.
For example if nvme_config::root_only was set, the cell attribute
would still provide read access to everybody.

Mask out permissions not available on the main attribute.

Fixes: 0331c611949f ("nvmem: core: Expose cells through sysfs")
Cc: stable@...r.kernel.org
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
This was also discussed as part of
"[PATCH] nvmem: core: add sysfs cell write support" [0].
But there haven't been updates to that patch and this is arguably a
standalone bugfix.

[0] https://lore.kernel.org/lkml/20240223154129.1902905-1-m.felsch@pengutronix.de/
---
 drivers/nvmem/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index e1ec3b7200d7..acfea1e56849 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -463,7 +463,7 @@ static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
 						    "%s@%x,%x", entry->name,
 						    entry->offset,
 						    entry->bit_offset);
-		attrs[i].attr.mode = 0444;
+		attrs[i].attr.mode = 0444 & nvmem_bin_attr_get_umode(nvmem);
 		attrs[i].size = entry->bytes;
 		attrs[i].read = &nvmem_cell_attr_read;
 		attrs[i].private = entry;

---
base-commit: 92e5605a199efbaee59fb19e15d6cc2103a04ec2
change-id: 20240619-nvmem-cell-sysfs-perm-156fde0d7460

Best regards,
-- 
Thomas Weißschuh <linux@...ssschuh.net>