Re: [PATCH v4 3/8] audit: add filtering for io_uring records

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(a)paul-moore.com&gt;

--- 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;