6.18-stable review patch. If anyone has any objections, please let me know.
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From: Konstantin Andreev andreev@swemel.ru
[ Upstream commit c147e13ea7fe9f118f8c9ba5e96cbd644b00d6b3 ]
If an unprivileged task is allowed to relabel itself (/smack/relabel-self is not empty), it can freely create new labels by writing their names into own /proc/PID/attr/smack/current
This occurs because do_setattr() imports the provided label in advance, before checking "relabel-self" list.
This change ensures that the "relabel-self" list is checked before importing the label.
Fixes: 38416e53936e ("Smack: limited capability for changing process label") 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/smack_lsm.c | 41 +++++++++++++++++++++++++------------- 1 file changed, 27 insertions(+), 14 deletions(-)
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index d16453801a79e..07dbc4cd303a7 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -3778,8 +3778,8 @@ static int do_setattr(u64 attr, void *value, size_t size) struct task_smack *tsp = smack_cred(current_cred()); struct cred *new; struct smack_known *skp; - struct smack_known_list_elem *sklep; - int rc; + char *labelstr; + int rc = 0;
if (!smack_privileged(CAP_MAC_ADMIN) && list_empty(&tsp->smk_relabel)) return -EPERM; @@ -3790,28 +3790,41 @@ static int do_setattr(u64 attr, void *value, size_t size) if (attr != LSM_ATTR_CURRENT) return -EOPNOTSUPP;
- skp = smk_import_entry(value, size); - if (IS_ERR(skp)) - return PTR_ERR(skp); + labelstr = smk_parse_smack(value, size); + if (IS_ERR(labelstr)) + return PTR_ERR(labelstr);
/* * No process is ever allowed the web ("@") label * and the star ("*") label. */ - if (skp == &smack_known_web || skp == &smack_known_star) - return -EINVAL; + if (labelstr[1] == '\0' /* '@', '*' */) { + const char c = labelstr[0]; + + if (c == *smack_known_web.smk_known || + c == *smack_known_star.smk_known) { + rc = -EPERM; + goto free_labelstr; + } + }
if (!smack_privileged(CAP_MAC_ADMIN)) { - rc = -EPERM; + const struct smack_known_list_elem *sklep; list_for_each_entry(sklep, &tsp->smk_relabel, list) - if (sklep->smk_label == skp) { - rc = 0; - break; - } - if (rc) - return rc; + if (strcmp(sklep->smk_label->smk_known, labelstr) == 0) + goto free_labelstr; + rc = -EPERM; }
+free_labelstr: + kfree(labelstr); + if (rc) + return -EPERM; + + skp = smk_import_entry(value, size); + if (IS_ERR(skp)) + return PTR_ERR(skp); + new = prepare_creds(); if (new == NULL) return -ENOMEM;