linux-kernel - Re: [RFC PATCH v3 2/2] security/inode.c: Add capabilities file.

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Date:   Fri, 21 Jan 2022 09:58:34 +0100
From:   Francis Laniel <flaniel@...ux.microsoft.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org,
        Serge Hallyn <serge@...lyn.com>,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [RFC PATCH v3 2/2] security/inode.c: Add capabilities file.

Hi.

Le jeudi 20 janvier 2022, 19:01:16 CET Francis Laniel a écrit :
> This new read-only file prints the capabilities values with their names:
> cat /sys/kernel/security/capabilities
> 0       CAP_CHOWN
> 1       CAP_DAC_OVERRIDE
> ...
> 40      CAP_CHECKPOINT_RESTORE
> 
> Signed-off-by: Francis Laniel <flaniel@...ux.microsoft.com>
> ---
>  security/inode.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/security/inode.c b/security/inode.c
> index 6c326939750d..cef78b497bab 100644
> --- a/security/inode.c
> +++ b/security/inode.c
> @@ -21,6 +21,7 @@
>  #include <linux/security.h>
>  #include <linux/lsm_hooks.h>
>  #include <linux/magic.h>
> +#include <linux/capability.h>
> 
>  static struct vfsmount *mount;
>  static int mount_count;
> @@ -328,6 +329,19 @@ static const struct file_operations lsm_ops = {
>  };
>  #endif
> 
> +static struct dentry *capabilities_dentry;
> +static ssize_t capabilities_read(struct file *unused, char __user *buf,
> +				 size_t count, loff_t *ppos)
> +{
> +	return simple_read_from_buffer(buf, count, ppos, cap_string,
> +				       strlen(cap_string));
> +}
> +
> +static const struct file_operations capabilities_ops = {
> +	.read = capabilities_read,
> +	.llseek = generic_file_llseek,
> +};
> +
>  static int __init securityfs_init(void)
>  {
>  	int retval;
> @@ -345,6 +359,8 @@ static int __init securityfs_init(void)
>  	lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
>  						&lsm_ops);
>  #endif
> +	capabilities_dentry = securityfs("capabilities", 0444, NULL, NULL,
> +					 capabilities_ops);

Sorry, I sent the old version of the patch and did not fixup this...
Kernel robot kindly show me this error.
I swear the output in the cover letter was done on the compiled kernel within 
a VM.

I will send a v4 correcting this but I will wait to get some reviews on v3 to 
not send to not generate too much traffic here.

>  	return 0;
>  }
>  core_initcall(securityfs_init);

Best regards.