linux-kernel - [PATCH] Smack: Restore the smackfsdef mount option and add missing prefixes

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Message-ID: <155907646050.25083.16573974978890009010.stgit@warthog.procyon.org.uk>
Date:   Tue, 28 May 2019 21:47:40 +0100
From:   David Howells <dhowells@...hat.com>
To:     casey@...aufler-ca.com
Cc:     dhowells@...hat.com, viro@...iv.linux.org.uk, jmorris@...ei.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Smack: Restore the smackfsdef mount option and add missing
 prefixes

From: Casey Schaufler <casey@...aufler-ca.com>

The 5.1 mount system rework changed the smackfsdef mount option
to smackfsdefault. This fixes the regression by making smackfsdef
treated the same way as smackfsdefault.

Also fix the smack_param_specs[] to have "smack" prefixes on all the names.
This isn't visible to a user unless they either:

 (a) Try to mount a filesystem that's converted to the internal mount API
     and that implements the ->parse_monolithic() context operation - and
     only then if they call security_fs_context_parse_param() rather than
     security_sb_eat_lsm_opts().

     There are no examples of this upstream yet, but nfs will probably want
     to do this for nfs2 or nfs3.

 (b) Use fsconfig() to configure the filesystem - in which case
     security_fs_context_parse_param() will be called.

This issue is that smack_sb_eat_lsm_opts() checks for the "smack" prefix on
the options, but smack_fs_context_parse_param() does not.

Fixes: c3300aaf95fb ("smack: get rid of match_token()")
Fixes: 2febd254adc4 ("smack: Implement filesystem context security hooks")
Cc: stable@...r.kernel.org
Reported-by: Jose Bollo <jose.bollo@....bzh>
Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 security/smack/smack_lsm.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 0de725f88bed..d99450b4f511 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -68,6 +68,7 @@ static struct {
 	int len;
 	int opt;
 } smk_mount_opts[] = {
+	{"smackfsdef", sizeof("smackfsdef") - 1, Opt_fsdefault},
 	A(fsdefault), A(fsfloor), A(fshat), A(fsroot), A(fstransmute)
 };
 #undef A
@@ -682,11 +683,12 @@ static int smack_fs_context_dup(struct fs_context *fc,
 }
 
 static const struct fs_parameter_spec smack_param_specs[] = {
-	fsparam_string("fsdefault",	Opt_fsdefault),
-	fsparam_string("fsfloor",	Opt_fsfloor),
-	fsparam_string("fshat",		Opt_fshat),
-	fsparam_string("fsroot",	Opt_fsroot),
-	fsparam_string("fstransmute",	Opt_fstransmute),
+	fsparam_string("smackfsdef",		Opt_fsdefault),
+	fsparam_string("smackfsdefault",	Opt_fsdefault),
+	fsparam_string("smackfsfloor",		Opt_fsfloor),
+	fsparam_string("smackfshat",		Opt_fshat),
+	fsparam_string("smackfsroot",		Opt_fsroot),
+	fsparam_string("smackfstransmute",	Opt_fstransmute),
 	{}
 };