lkml.org 
[lkml]   [2020]   [Apr]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 3/3 RESEND] auditsc: Do not use RCU primitive to read from cred pointer
On Thu, Apr 2, 2020 at 1:57 AM Amol Grover <frextrite@gmail.com> wrote:
> 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@google.com>
> Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> Signed-off-by: Amol Grover <frextrite@gmail.com>
> ---
> kernel/auditsc.c | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)

This is the exact same patch I ACK'd back in February, yes?

https://lore.kernel.org/linux-audit/CAHC9VhQCbg1V290bYEZM+izDPRpr=XYXakohnDaMphkBBFgUaA@mail.gmail.com

> 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

--
paul moore
www.paul-moore.com

\
 
 \ /
  Last update: 2020-04-02 14:57    [W:0.279 / U:0.848 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site