[PATCH 6.6 085/283] smack: /smack/doi: accept previously used values

Sasha Levin
2026-02-28T18:08:19Z

From: Konstantin Andreev <andreev@swemel.ru>

[ Upstream commit 33d589ed60ae433b483761987b85e0d24e54584e ]

Writing to /smack/doi a value that has ever been
written there in the past disables networking for
non-ambient labels.
E.g.

# cat /smack/doi
3
# netlabelctl -p cipso list
Configured CIPSO mappings (1)
DOI value : 3
mapping type : PASS_THROUGH
# netlabelctl -p map list
Configured NetLabel domain mappings (3)
domain: "_" (IPv4)
protocol: UNLABELED
domain: DEFAULT (IPv4)
protocol: CIPSO, DOI = 3
domain: DEFAULT (IPv6)
protocol: UNLABELED

# cat /smack/ambient
_
# cat /proc/$$/attr/smack/current
_
# ping -c1 10.1.95.12
64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.964 ms
# echo foo >/proc/$$/attr/smack/current
# ping -c1 10.1.95.12
64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.956 ms
unknown option 86

# echo 4 >/smack/doi
# echo 3 >/smack/doi
!> [ 214.050395] smk_cipso_doi:691 cipso add rc = -17
# echo 3 >/smack/doi
!> [ 249.402261] smk_cipso_doi:678 remove rc = -2
!> [ 249.402261] smk_cipso_doi:691 cipso add rc = -17

# ping -c1 10.1.95.12
!!> ping: 10.1.95.12: Address family for hostname not supported

# echo _ >/proc/$$/attr/smack/current
# ping -c1 10.1.95.12
64 bytes from 10.1.95.12: icmp_seq=1 ttl=64 time=0.617 ms

This happens because Smack keeps decommissioned DOIs,
fails to re-add them, and consequently refuses to add
the “default” domain map:

# netlabelctl -p cipso list
Configured CIPSO mappings (2)
DOI value : 3
mapping type : PASS_THROUGH
DOI value : 4
mapping type : PASS_THROUGH
# netlabelctl -p map list
Configured NetLabel domain mappings (2)
domain: "_" (IPv4)
protocol: UNLABELED
!> (no ipv4 map for default domain here)
domain: DEFAULT (IPv6)
protocol: UNLABELED

Fix by clearing decommissioned DOI definitions and
serializing concurrent DOI updates with a new lock.

Also:
- allow /smack/doi to live unconfigured, since
adding a map (netlbl_cfg_cipsov4_map_add) may fail.
CIPSO_V4_DOI_UNKNOWN(0) indicates the unconfigured DOI
- add new DOI before removing the old default map,
so the old map remains if the add fails

(2008-02-04, Casey Schaufler)
Fixes: e114e473771c ("Smack: Simplified Mandatory Access Control Kernel")

Signed-off-by: Konstantin Andreev <andreev@swemel.ru>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
security/smack/smackfs.c | 71 +++++++++++++++++++++++++---------------
1 file changed, 45 insertions(+), 26 deletions(-)

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index a130007397562..109ad155ffc2a 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -68,6 +68,7 @@ enum smk_inos {
static DEFINE_MUTEX(smack_cipso_lock);
static DEFINE_MUTEX(smack_ambient_lock);
static DEFINE_MUTEX(smk_net4addr_lock);
+static DEFINE_MUTEX(smk_cipso_doi_lock);
#if IS_ENABLED(CONFIG_IPV6)
static DEFINE_MUTEX(smk_net6addr_lock);
#endif /* CONFIG_IPV6 */
@@ -139,7 +140,7 @@ struct smack_parsed_rule {
int smk_access2;
};

-static u32 smk_cipso_doi_value = SMACK_CIPSO_DOI_DEFAULT;
+static u32 smk_cipso_doi_value = CIPSO_V4_DOI_UNKNOWN;

/*
* Values for parsing cipso rules
@@ -679,43 +680,60 @@ static const struct file_operations smk_load_ops = {
};

/**
- * smk_cipso_doi - initialize the CIPSO domain
+ * smk_cipso_doi - set netlabel maps
+ * @ndoi: new value for our CIPSO DOI
+ * @gfp_flags: kmalloc allocation context
*/
-static void smk_cipso_doi(void)
+static int
+smk_cipso_doi(u32 ndoi, gfp_t gfp_flags)
{
- int rc;
+ int rc = 0;
struct cipso_v4_doi *doip;
struct netlbl_audit nai;

- smk_netlabel_audit_set(&nai);
+ mutex_lock(&smk_cipso_doi_lock);

- rc = netlbl_cfg_map_del(NULL, PF_INET, NULL, NULL, &nai);
- if (rc != 0)
- printk(KERN_WARNING "%s:%d remove rc = %d\n",
- __func__, __LINE__, rc);
+ if (smk_cipso_doi_value == ndoi)
+ goto clr_doi_lock;
+
+ smk_netlabel_audit_set(&nai);

- doip = kmalloc(sizeof(struct cipso_v4_doi), GFP_KERNEL | __GFP_NOFAIL);
+ doip = kmalloc(sizeof(struct cipso_v4_doi), gfp_flags);
+ if (!doip) {
+ rc = -ENOMEM;
+ goto clr_doi_lock;
+ }
doip->map.std = NULL;
- doip->doi = smk_cipso_doi_value;
+ doip->doi = ndoi;
doip->type = CIPSO_V4_MAP_PASS;
doip->tags[0] = CIPSO_V4_TAG_RBITMAP;
for (rc = 1; rc < CIPSO_V4_TAG_MAXCNT; rc++)
doip->tags[rc] = CIPSO_V4_TAG_INVALID;

rc = netlbl_cfg_cipsov4_add(doip, &nai);
- if (rc != 0) {
- printk(KERN_WARNING "%s:%d cipso add rc = %d\n",
- __func__, __LINE__, rc);
+ if (rc) {
kfree(doip);
- return;
+ goto clr_doi_lock;
}
- rc = netlbl_cfg_cipsov4_map_add(doip->doi, NULL, NULL, NULL, &nai);
- if (rc != 0) {
- printk(KERN_WARNING "%s:%d map add rc = %d\n",
- __func__, __LINE__, rc);
- netlbl_cfg_cipsov4_del(doip->doi, &nai);
- return;
+
+ if (smk_cipso_doi_value != CIPSO_V4_DOI_UNKNOWN) {
+ rc = netlbl_cfg_map_del(NULL, PF_INET, NULL, NULL, &nai);
+ if (rc && rc != -ENOENT)
+ goto clr_ndoi_def;
+
+ netlbl_cfg_cipsov4_del(smk_cipso_doi_value, &nai);
}
+
+ rc = netlbl_cfg_cipsov4_map_add(ndoi, NULL, NULL, NULL, &nai);
+ if (rc) {
+ smk_cipso_doi_value = CIPSO_V4_DOI_UNKNOWN; // no default map
+clr_ndoi_def: netlbl_cfg_cipsov4_del(ndoi, &nai);
+ } else
+ smk_cipso_doi_value = ndoi;
+
+clr_doi_lock:
+ mutex_unlock(&smk_cipso_doi_lock);
+ return rc;
}

/**
@@ -1617,11 +1635,8 @@ static ssize_t smk_write_doi(struct file *file, const char __user *buf,

if (u == CIPSO_V4_DOI_UNKNOWN || u > U32_MAX)
return -EINVAL;
- smk_cipso_doi_value = u;
-
- smk_cipso_doi();

- return count;
+ return smk_cipso_doi(u, GFP_KERNEL) ? : count;
}

static const struct file_operations smk_doi_ops = {
@@ -2998,6 +3013,7 @@ static int __init init_smk_fs(void)
{
int err;
int rc;
+ struct netlbl_audit nai;

if (smack_enabled == 0)
return 0;
@@ -3016,7 +3032,10 @@ static int __init init_smk_fs(void)
}
}

- smk_cipso_doi();
+ smk_netlabel_audit_set(&nai);
+ (void) netlbl_cfg_map_del(NULL, PF_INET, NULL, NULL, &nai);
+ (void) smk_cipso_doi(SMACK_CIPSO_DOI_DEFAULT,
+ GFP_KERNEL | __GFP_NOFAIL);
smk_unlbl_ambient(NULL);

rc = smack_populate_secattr(&smack_known_floor);
--
2.51.0