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

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Date: Sat, 22 Jun 2024 11:10:58 +0100
From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To: Thomas Weißschuh <linux@...ssschuh.net>,
 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
Subject: Re: [PATCH] nvmem: core: limit cell sysfs permissions to main
 attribute ones



On 19/06/2024 19:09, Thomas Weißschuh wrote:
> 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);
Why not just
attrs[i].attr.mode = nvmem_bin_attr_get_umode(nvmem);
?

--srini
>   		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,