linux-kernel - Re: [PATCH] security: new security_file_ioctl

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Date: Sat, 23 Dec 2023 19:48:58 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Paul Moore <paul@...l-moore.com>, Alfred Piccioni <alpic@...gle.com>
Cc: Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        linux-security-module@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        stable@...r.kernel.org, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org, Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH] security: new security_file_ioctl_compat() hook

On 2023/12/23 10:23, Paul Moore wrote:
>> -       /* RED-PEN how should LSM module know it's handling 32bit? */
>> -       error = security_file_ioctl(f.file, cmd, arg);
>> +       error = security_file_ioctl_compat(f.file, cmd, arg);
>>         if (error)
>>                 goto out;
> 
> This is interesting ... if you look at the normal ioctl() syscall
> definition in the kernel you see 'ioctl(unsigned int fd, unsigned int
> cmd, unsigned long arg)' and if you look at the compat definition you
> see 'ioctl(unsigned int fd, unsigned int cmd, compat_ulong_t arg)'.  I
> was expecting the second parameter, @cmd, to be a long type in the
> normal definition, but it is an int type in both cases.  It looks like
> it has been that way long enough that it is correct, but I'm a little
> lost ...

Since @arg might be a pointer to some struct, @arg needs to use a long type.
But @cmd can remain 32bits for both 32bits/64bits kernels because @cmd is not
a pointer, can't it?

> I agree that it looks like Smack and TOMOYO should be fine, but I
> would like to hear from Casey and Tetsuo to confirm.

Fine for TOMOYO part, for TOMOYO treats @cmd as an integer.