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authorJann Horn <jannh@google.com>2019-04-11 23:11:54 +0300
committerMicah Morton <mortonm@chromium.org>2019-07-15 18:07:40 +0300
commitfbd9acb2dc2aa55902c48a83f157082849209fba (patch)
treed679fe88f9abdf52198a72397d7116d970fce953
parent03638e62f55f27e7a96d6b1175e75b7a81e562b3 (diff)
downloadlinux-fbd9acb2dc2aa55902c48a83f157082849209fba.tar.xz
LSM: SafeSetID: add read handler
For debugging a running system, it is very helpful to be able to see what policy the system is using. Add a read handler that can dump out a copy of the loaded policy. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
-rw-r--r--security/safesetid/lsm.h1
-rw-r--r--security/safesetid/securityfs.c35
2 files changed, 32 insertions, 4 deletions
diff --git a/security/safesetid/lsm.h b/security/safesetid/lsm.h
index 4a34f558d964..db6d16e6bbc3 100644
--- a/security/safesetid/lsm.h
+++ b/security/safesetid/lsm.h
@@ -41,6 +41,7 @@ struct setuid_rule {
struct setuid_ruleset {
DECLARE_HASHTABLE(rules, SETID_HASH_BITS);
+ char *policy_str;
struct rcu_head rcu;
};
diff --git a/security/safesetid/securityfs.c b/security/safesetid/securityfs.c
index 250d59e046c1..997b403c6255 100644
--- a/security/safesetid/securityfs.c
+++ b/security/safesetid/securityfs.c
@@ -19,7 +19,7 @@
#include "lsm.h"
-static DEFINE_SPINLOCK(policy_update_lock);
+static DEFINE_MUTEX(policy_update_lock);
/*
* In the case the input buffer contains one or more invalid UIDs, the kuid_t
@@ -67,6 +67,7 @@ static void __release_ruleset(struct rcu_head *rcu)
hash_for_each_safe(pol->rules, bucket, tmp, rule, next)
kfree(rule);
+ kfree(pol->policy_str);
kfree(pol);
}
@@ -85,6 +86,7 @@ static ssize_t handle_policy_update(struct file *file,
pol = kmalloc(sizeof(struct setuid_ruleset), GFP_KERNEL);
if (!pol)
return -ENOMEM;
+ pol->policy_str = NULL;
hash_init(pol->rules);
p = buf = memdup_user_nul(ubuf, len);
@@ -92,6 +94,11 @@ static ssize_t handle_policy_update(struct file *file,
err = PTR_ERR(buf);
goto out_free_pol;
}
+ pol->policy_str = kstrdup(buf, GFP_KERNEL);
+ if (pol->policy_str == NULL) {
+ err = -ENOMEM;
+ goto out_free_buf;
+ }
/* policy lines, including the last one, end with \n */
while (*p != '\0') {
@@ -135,10 +142,10 @@ out_free_rule:
* What we really want here is an xchg() wrapper for RCU, but since that
* doesn't currently exist, just use a spinlock for now.
*/
- spin_lock(&policy_update_lock);
+ mutex_lock(&policy_update_lock);
rcu_swap_protected(safesetid_setuid_rules, pol,
lockdep_is_held(&policy_update_lock));
- spin_unlock(&policy_update_lock);
+ mutex_unlock(&policy_update_lock);
err = len;
out_free_buf:
@@ -162,7 +169,27 @@ static ssize_t safesetid_file_write(struct file *file,
return handle_policy_update(file, buf, len);
}
+static ssize_t safesetid_file_read(struct file *file, char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ ssize_t res = 0;
+ struct setuid_ruleset *pol;
+ const char *kbuf;
+
+ mutex_lock(&policy_update_lock);
+ pol = rcu_dereference_protected(safesetid_setuid_rules,
+ lockdep_is_held(&policy_update_lock));
+ if (pol) {
+ kbuf = pol->policy_str;
+ res = simple_read_from_buffer(buf, len, ppos,
+ kbuf, strlen(kbuf));
+ }
+ mutex_unlock(&policy_update_lock);
+ return res;
+}
+
static const struct file_operations safesetid_file_fops = {
+ .read = safesetid_file_read,
.write = safesetid_file_write,
};
@@ -181,7 +208,7 @@ static int __init safesetid_init_securityfs(void)
goto error;
}
- policy_file = securityfs_create_file("whitelist_policy", 0200,
+ policy_file = securityfs_create_file("whitelist_policy", 0600,
policy_dir, NULL, &safesetid_file_fops);
if (IS_ERR(policy_file)) {
ret = PTR_ERR(policy_file);