linux-kernel - Re: [RESEND v5 2/4] fs: debugfs: Add write functionality to debugfs blobs

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Message-ID: <71ad8b0e-984b-4739-a940-82c5a1456f50@amd.com>
Date:   Thu, 16 Nov 2023 11:54:17 -0600
From:   Avadhut Naik <avadnaik@....com>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     "rafael@...nel.org" <rafael@...nel.org>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "james.morse@....com" <james.morse@....com>,
        "bp@...en8.de" <bp@...en8.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "alexey.kardashevskiy@....com" <alexey.kardashevskiy@....com>,
        "yazen.ghannam@....com" <yazen.ghannam@....com>,
        Avadhut Naik <avadhut.naik@....com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [RESEND v5 2/4] fs: debugfs: Add write functionality to debugfs
 blobs

Hi Tony,

On 11/7/2023 16:28, Luck, Tony wrote:
>> @@ -1042,7 +1060,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode,
>> 				   struct dentry *parent,
>> 				   struct debugfs_blob_wrapper *blob)
>> {
>> -	return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob);
>> +	return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob);
>> }
> 
> The minimalist change here would be to s/0444/0666/
> 
Just realized that s/0444/0644/ might be an even more minimalist change since you anyways,
I think, need to be root for error injection through einj. Does that sound good?

In any case, using 0666 will result in the below checkpatch warning:

[root avadnaik-linux]# ./scripts/checkpatch.pl --strict -g HEAD
WARNING: Exporting world writable files is usually an error. Consider more restrictive permissions.
#84: FILE: fs/debugfs/file.c:1063:
+       return debugfs_create_file_unsafe(name, mode & 0666, parent, blob, &fops_blob);

total: 0 errors, 1 warnings, 0 checks, 54 lines checked

Would you be okay with s/0444/0644/?

-       return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob);
+       return debugfs_create_file_unsafe(name, mode & 0644, parent, blob, &fops_blob);

> That would just allow callers to ask for writeable files without letting them
> add execute permission, or exotic modes like setuid etc.
> 
> -Tony

-- 
Thanks,
Avadhut Naik