[PATCH 3/3] auditsc: Do not use RCU primitive to read from cred pointer
task_struct::cred is only used task-synchronously and does
not require any RCU locks, hence, rcu_dereference_check is
not required to read from it.
Suggested-by: Jann Horn <jannh(a)google.com>
Co-developed-by: Joel Fernandes (Google) <joel(a)joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel(a)joelfernandes.org>
Signed-off-by: Amol Grover <frextrite(a)gmail.com>
---
kernel/auditsc.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 4effe01ebbe2..d3510513cdd1 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -430,24 +430,19 @@ static int audit_field_compare(struct task_struct *tsk,
/* Determine if any context name data matches a rule's watch data */
/* Compare a task_struct with an audit_rule. Return 1 on match, 0
* otherwise.
- *
- * If task_creation is true, this is an explicit indication that we are
- * filtering a task rule at task creation time. This and tsk == current are
- * the only situations where tsk->cred may be accessed without an rcu read lock.
*/
static int audit_filter_rules(struct task_struct *tsk,
struct audit_krule *rule,
struct audit_context *ctx,
struct audit_names *name,
- enum audit_state *state,
- bool task_creation)
+ enum audit_state *state)
{
const struct cred *cred;
int i, need_sid = 1;
u32 sid;
unsigned int sessionid;
- cred = rcu_dereference_check(tsk->cred, tsk == current || task_creation);
+ cred = tsk->cred;
for (i = 0; i < rule->field_count; i++) {
struct audit_field *f = &rule->fields[i];
@@ -745,7 +740,7 @@ static enum audit_state audit_filter_task(struct task_struct *tsk,
char **key)
rcu_read_lock();
list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TASK], list) {
if (audit_filter_rules(tsk, &e->rule, NULL, NULL,
- &state, true)) {
+ &state)) {
if (state == AUDIT_RECORD_CONTEXT)
*key = kstrdup(e->rule.filterkey, GFP_ATOMIC);
rcu_read_unlock();
@@ -791,7 +786,7 @@ static enum audit_state audit_filter_syscall(struct task_struct *tsk,
list_for_each_entry_rcu(e, list, list) {
if (audit_in_mask(&e->rule, ctx->major) &&
audit_filter_rules(tsk, &e->rule, ctx, NULL,
- &state, false)) {
+ &state)) {
rcu_read_unlock();
ctx->current_state = state;
return state;
@@ -815,7 +810,7 @@ static int audit_filter_inode_name(struct task_struct *tsk,
list_for_each_entry_rcu(e, list, list) {
if (audit_in_mask(&e->rule, ctx->major) &&
- audit_filter_rules(tsk, &e->rule, ctx, n, &state, false)) {
+ audit_filter_rules(tsk, &e->rule, ctx, n, &state)) {
ctx->current_state = state;
return 1;
}
--
2.24.1