On 2021-09-15 12:49, Paul Moore wrote:
> This patch adds basic audit io_uring filtering, using as much of the
> existing audit filtering infrastructure as possible. In order to do
> this we reuse the audit filter rule's syscall mask for the io_uring
> operation and we create a new filter for io_uring operations as
> AUDIT_FILTER_URING_EXIT/audit_filter_list[7].
>
> Thanks to Richard Guy Briggs for his review, feedback, and work on
> the corresponding audit userspace changes.
>
> Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Looks good.
Acked-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> ---
> v4:
> - no change
> v3:
> - removed work-in-progress warning from the description
> v2:
> - incorporate feedback from Richard
> v1:
> - initial draft
> ---
> include/uapi/linux/audit.h | 3 +-
> kernel/audit_tree.c | 3 +-
> kernel/audit_watch.c | 3 +-
> kernel/auditfilter.c | 15 +++++++++--
> kernel/auditsc.c | 61 ++++++++++++++++++++++++++++++++++----------
> 5 files changed, 65 insertions(+), 20 deletions(-)
>
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index a1997697c8b1..ecf1edd2affa 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -167,8 +167,9 @@
> #define AUDIT_FILTER_EXCLUDE 0x05 /* Apply rule before record creation */
> #define AUDIT_FILTER_TYPE AUDIT_FILTER_EXCLUDE /* obsolete misleading naming */
> #define AUDIT_FILTER_FS 0x06 /* Apply rule at __audit_inode_child */
> +#define AUDIT_FILTER_URING_EXIT 0x07 /* Apply rule at io_uring op exit */
>
> -#define AUDIT_NR_FILTERS 7
> +#define AUDIT_NR_FILTERS 8
>
> #define AUDIT_FILTER_PREPEND 0x10 /* Prepend to front of list */
>
> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index 2cd7b5694422..338c53a961c5 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -726,7 +726,8 @@ int audit_make_tree(struct audit_krule *rule, char *pathname, u32 op)
> {
>
> if (pathname[0] != '/' ||
> - rule->listnr != AUDIT_FILTER_EXIT ||
> + (rule->listnr != AUDIT_FILTER_EXIT &&
> + rule->listnr != AUDIT_FILTER_URING_EXIT) ||
> op != Audit_equal ||
> rule->inode_f || rule->watch || rule->tree)
> return -EINVAL;
> diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
> index 2acf7ca49154..698b62b4a2ec 100644
> --- a/kernel/audit_watch.c
> +++ b/kernel/audit_watch.c
> @@ -183,7 +183,8 @@ int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
> return -EOPNOTSUPP;
>
> if (path[0] != '/' || path[len-1] == '/' ||
> - krule->listnr != AUDIT_FILTER_EXIT ||
> + (krule->listnr != AUDIT_FILTER_EXIT &&
> + krule->listnr != AUDIT_FILTER_URING_EXIT) ||
> op != Audit_equal ||
> krule->inode_f || krule->watch || krule->tree)
> return -EINVAL;
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index db2c6b59dfc3..d75acb014ccd 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -44,7 +44,8 @@ struct list_head audit_filter_list[AUDIT_NR_FILTERS] = {
> LIST_HEAD_INIT(audit_filter_list[4]),
> LIST_HEAD_INIT(audit_filter_list[5]),
> LIST_HEAD_INIT(audit_filter_list[6]),
> -#if AUDIT_NR_FILTERS != 7
> + LIST_HEAD_INIT(audit_filter_list[7]),
> +#if AUDIT_NR_FILTERS != 8
> #error Fix audit_filter_list initialiser
> #endif
> };
> @@ -56,6 +57,7 @@ static struct list_head audit_rules_list[AUDIT_NR_FILTERS] = {
> LIST_HEAD_INIT(audit_rules_list[4]),
> LIST_HEAD_INIT(audit_rules_list[5]),
> LIST_HEAD_INIT(audit_rules_list[6]),
> + LIST_HEAD_INIT(audit_rules_list[7]),
> };
>
> DEFINE_MUTEX(audit_filter_mutex);
> @@ -151,7 +153,8 @@ char *audit_unpack_string(void **bufp, size_t *remain, size_t len)
> static inline int audit_to_inode(struct audit_krule *krule,
> struct audit_field *f)
> {
> - if (krule->listnr != AUDIT_FILTER_EXIT ||
> + if ((krule->listnr != AUDIT_FILTER_EXIT &&
> + krule->listnr != AUDIT_FILTER_URING_EXIT) ||
> krule->inode_f || krule->watch || krule->tree ||
> (f->op != Audit_equal && f->op != Audit_not_equal))
> return -EINVAL;
> @@ -248,6 +251,7 @@ static inline struct audit_entry *audit_to_entry_common(struct audit_rule_data *
> pr_err("AUDIT_FILTER_ENTRY is deprecated\n");
> goto exit_err;
> case AUDIT_FILTER_EXIT:
> + case AUDIT_FILTER_URING_EXIT:
> case AUDIT_FILTER_TASK:
> #endif
> case AUDIT_FILTER_USER:
> @@ -332,6 +336,10 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
> if (entry->rule.listnr != AUDIT_FILTER_FS)
> return -EINVAL;
> break;
> + case AUDIT_PERM:
> + if (entry->rule.listnr == AUDIT_FILTER_URING_EXIT)
> + return -EINVAL;
> + break;
> }
>
> switch (entry->rule.listnr) {
> @@ -980,7 +988,8 @@ static inline int audit_add_rule(struct audit_entry *entry)
> }
>
> entry->rule.prio = ~0ULL;
> - if (entry->rule.listnr == AUDIT_FILTER_EXIT) {
> + if (entry->rule.listnr == AUDIT_FILTER_EXIT ||
> + entry->rule.listnr == AUDIT_FILTER_URING_EXIT) {
> if (entry->rule.flags & AUDIT_FILTER_PREPEND)
> entry->rule.prio = ++prio_high;
> else
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 6dda448fb826..7c66a9fea5e6 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -805,6 +805,35 @@ static int audit_in_mask(const struct audit_krule *rule, unsigned long val)
> return rule->mask[word] & bit;
> }
>
> +/**
> + * audit_filter_uring - apply filters to an io_uring operation
> + * @tsk: associated task
> + * @ctx: audit context
> + */
> +static void audit_filter_uring(struct task_struct *tsk,
> + struct audit_context *ctx)
> +{
> + struct audit_entry *e;
> + enum audit_state state;
> +
> + if (auditd_test_task(tsk))
> + return;
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_URING_EXIT],
> + list) {
> + if (audit_in_mask(&e->rule, ctx->uring_op) &&
> + audit_filter_rules(tsk, &e->rule, ctx, NULL, &state,
> + false)) {
> + rcu_read_unlock();
> + ctx->current_state = state;
> + return;
> + }
> + }
> + rcu_read_unlock();
> + return;
> +}
> +
> /* At syscall exit time, this filter is called if the audit_state is
> * not low enough that auditing cannot take place, but is also not
> * high enough that we already know we have to write an audit record
> @@ -1757,7 +1786,7 @@ static void audit_log_exit(void)
> * __audit_free - free a per-task audit context
> * @tsk: task whose audit context block to free
> *
> - * Called from copy_process and do_exit
> + * Called from copy_process, do_exit, and the io_uring code
> */
> void __audit_free(struct task_struct *tsk)
> {
> @@ -1775,15 +1804,21 @@ void __audit_free(struct task_struct *tsk)
> * random task_struct that doesn't doesn't have any meaningful data we
> * need to log via audit_log_exit().
> */
> - if (tsk == current && !context->dummy &&
> - context->context == AUDIT_CTX_SYSCALL) {
> + if (tsk == current && !context->dummy) {
> context->return_valid = AUDITSC_INVALID;
> context->return_code = 0;
> -
> - audit_filter_syscall(tsk, context);
> - audit_filter_inodes(tsk, context);
> - if (context->current_state == AUDIT_STATE_RECORD)
> - audit_log_exit();
> + if (context->context == AUDIT_CTX_SYSCALL) {
> + audit_filter_syscall(tsk, context);
> + audit_filter_inodes(tsk, context);
> + if (context->current_state == AUDIT_STATE_RECORD)
> + audit_log_exit();
> + } else if (context->context == AUDIT_CTX_URING) {
> + /* TODO: verify this case is real and valid */
> + audit_filter_uring(tsk, context);
> + audit_filter_inodes(tsk, context);
> + if (context->current_state == AUDIT_STATE_RECORD)
> + audit_log_uring(context);
> + }
> }
>
> audit_set_context(tsk, NULL);
> @@ -1867,12 +1902,6 @@ void __audit_uring_exit(int success, long code)
> {
> struct audit_context *ctx = audit_context();
>
> - /*
> - * TODO: At some point we will likely want to filter on io_uring ops
> - * and other things similar to what we do for syscalls, but that
> - * is something for another day; just record what we can here.
> - */
> -
> if (ctx->context == AUDIT_CTX_SYSCALL) {
> /*
> * NOTE: See the note in __audit_uring_entry() about the case
> @@ -1895,6 +1924,8 @@ void __audit_uring_exit(int success, long code)
> * the behavior here.
> */
> audit_filter_syscall(current, ctx);
> + if (ctx->current_state != AUDIT_STATE_RECORD)
> + audit_filter_uring(current, ctx);
> audit_filter_inodes(current, ctx);
> if (ctx->current_state != AUDIT_STATE_RECORD)
> return;
> @@ -1907,6 +1938,8 @@ void __audit_uring_exit(int success, long code)
> if (!list_empty(&ctx->killed_trees))
> audit_kill_trees(ctx);
>
> + /* run through both filters to ensure we set the filterkey properly */
> + audit_filter_uring(current, ctx);
> audit_filter_inodes(current, ctx);
> if (ctx->current_state != AUDIT_STATE_RECORD)
> goto out;
>
- RGB
--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635
