linux-kernel - Re: [PATCH v21 6/6] samples/check-exec: Add an enlighten "inc" interpreter and 28 tests

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Message-ID: <20241122.ahY1pooz1ing@digikod.net>
Date: Fri, 22 Nov 2024 15:50:56 +0100
From: Mickaël Salaün <mic@...ikod.net>
To: Mimi Zohar <zohar@...ux.ibm.com>
Cc: Al Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Kees Cook <keescook@...omium.org>, 
	Paul Moore <paul@...l-moore.com>, Serge Hallyn <serge@...lyn.com>, 
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	Steve Grubb <sgrubb@...hat.com>, Theodore Ts'o <tytso@....edu>, 
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	linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH v21 6/6] samples/check-exec: Add an enlighten "inc"
 interpreter and 28 tests

On Thu, Nov 21, 2024 at 03:34:47PM -0500, Mimi Zohar wrote:
> Hi Mickaël,
> 
> On Tue, 2024-11-12 at 20:18 +0100, Mickaël Salaün wrote:
> > 
> > +
> > +/* Returns 1 on error, 0 otherwise. */
> > +static int interpret_stream(FILE *script, char *const script_name,
> > +			    char *const *const envp, const bool restrict_stream)
> > +{
> > +	int err;
> > +	char *const script_argv[] = { script_name, NULL };
> > +	char buf[128] = {};
> > +	size_t buf_size = sizeof(buf);
> > +
> > +	/*
> > +	 * We pass a valid argv and envp to the kernel to emulate a native
> > +	 * script execution.  We must use the script file descriptor instead of
> > +	 * the script path name to avoid race conditions.
> > +	 */
> > +	err = execveat(fileno(script), "", script_argv, envp,
> > +		       AT_EMPTY_PATH | AT_EXECVE_CHECK);
> 
> At least with v20, the AT_CHECK always was being set, independent of whether
> set-exec.c set it.  I'll re-test with v21.

AT_EXECVE_CEHCK should always be set, only the interpretation of the
result should be relative to securebits.  This is highlighted in the
documentation.

> 
> thanks,
> 
> Mimi
> 
> > +	if (err && restrict_stream) {
> > +		perror("ERROR: Script execution check");
> > +		return 1;
> > +	}
> > +
> > +	/* Reads script. */
> > +	buf_size = fread(buf, 1, buf_size - 1, script);
> > +	return interpret_buffer(buf, buf_size);
> > +}
> > +
> 
>