[PATCH] smack: /smack/doi: accept previously used values
Casey Schaufler
casey at schaufler-ca.com
Wed Dec 31 20:52:03 UTC 2025
On 9/30/2025 5:31 AM, Konstantin Andreev wrote:
> 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 at swemel.ru>
Added to smack-next for 6.20. Thank you.
> ---
> The patch is verified to work on top of "smack: /smack/doi must be > 0" patch.
> Link: https://lore.kernel.org/linux-security-module/20250930121602.138337-1-andreev@swemel.ru
>
> 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 316c2ea401e8..d27d9140dda2 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -70,6 +70,7 @@ 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 */
> @@ -141,7 +142,7 @@ 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
> @@ -663,43 +664,60 @@ 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;
>
> + mutex_lock(&smk_cipso_doi_lock);
> +
> + if (smk_cipso_doi_value == ndoi)
> + goto clr_doi_lock;
> +
> smk_netlabel_audit_set(&nai);
>
> - 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);
> -
> - 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;
> }
>
> /**
> @@ -1599,11 +1617,8 @@ 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 = {
> @@ -2984,6 +2999,7 @@ static int __init init_smk_fs(void)
> {
> int err;
> int rc;
> + struct netlbl_audit nai;
>
> if (smack_enabled == 0)
> return 0;
> @@ -3002,7 +3018,10 @@ 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);
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