linux-kernel - Re: [PATCH v2 2/2] lsm: Add/fix return values in lsm

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Date:   Thu, 08 Dec 2022 10:29:20 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     David Howells <dhowells@...hat.com>, casey@...aufler-ca.com,
        omosnace@...hat.com, john.johansen@...onical.com,
        kpsingh@...nel.org, bpf@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v2 2/2] lsm: Add/fix return values in lsm_hooks.h and
 fix formatting

On Wed, 2022-12-07 at 14:34 -0500, Paul Moore wrote:
> On Wed, Dec 7, 2022 at 4:18 AM Roberto Sassu
> <roberto.sassu@...weicloud.com> wrote:
> > For this patch, I saw it is already in lsm/next. Paul, should I do an
> > incremental patch or change the one in the repo and you force push it?
> > I would just remove the three lines after the parameters description.
> 
> Just send a patch against the current lsm/next branch to remove those
> lines, and please do it ASAP as the merge window opens this
> weekend/Monday.

Ok, was about to send but I would need a clarification first.

In mount_api.rst, there is for security_fs_context_parse_param():

     The value pointed to by param may be modified (if a string) or stolen
     (provided the value pointer is NULL'd out).  If it is stolen, 0 must be
     returned to prevent it being passed to the filesystem.

Looking at security.c:

	hlist_for_each_entry(hp, &security_hook_heads.fs_context_parse_param,
			     list) {
		trc = hp->hook.fs_context_parse_param(fc, param);
		if (trc == 0)
			rc = 0;
		else if (trc != -ENOPARAM)
			return trc;
	}

If, as mount_api.rst says, the value is modified by an LSM or stolen,
should it be passed to other LSMs too?

Thanks

Roberto