[RFC PATCH 17/24] pidfd: audit child spawn execution

[Li Chen <me@linux.beauty>]

The child exec path runs outside the caller's audit context. A delayed
filename can leave a name-only record in the caller transaction, but inode
metadata and exec arguments are otherwise lost because the new task starts
with an unused audit context.

Start a dedicated AUDIT_PIDFD_SPAWN transaction before executable lookup so
audit rules can observe child identity, EXECVE arguments, and inode-backed
PATH records. Close it explicitly with the child setup result.
Task work does not enter through a userspace syscall frame, so do not
synthesize one.

Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: Li Chen <me@linux.beauty>
---
 fs/pidfd_spawn.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/fs/pidfd_spawn.c b/fs/pidfd_spawn.c
index 41d5cbb49a0f7..5586926988406 100644
--- a/fs/pidfd_spawn.c
+++ b/fs/pidfd_spawn.c
@@ -3,6 +3,8 @@
  * pidfd-backed process spawn builders
  */
 
+#include <asm/syscall.h>
+#include <linux/audit.h>
 #include <linux/completion.h>
 #include <linux/cred.h>
 #include <linux/file.h>
@@ -81,6 +83,8 @@ struct pidfd_spawn_state {
 	char *staged_path;
 	struct user_arg_ptr argv;
 	struct user_arg_ptr envp;
+	unsigned long audit_args[4];
+	int audit_syscall;
 	int result;
 	enum pidfd_spawn_status status;
 };
@@ -206,6 +210,8 @@ static void pidfd_spawn_drop_run_data(struct pidfd_spawn_state *state,
 	state->staged_path = NULL;
 	state->argv = native_arg(NULL);
 	state->envp = native_arg(NULL);
+	memset(state->audit_args, 0, sizeof(state->audit_args));
+	state->audit_syscall = 0;
 	state->result = result;
 	pidfd_spawn_set_status(state, PIDFD_SPAWN_SETUP_DONE);
 	mutex_unlock(&state->lock);
@@ -377,6 +383,22 @@ SYSCALL_DEFINE5(pidfd_config, int, fd, unsigned int, cmd,
 	return ret;
 }
 
+static void pidfd_spawn_save_audit_context(struct pidfd_spawn_state *state)
+{
+	struct pt_regs *regs = current_pt_regs();
+	unsigned long args[6];
+
+	syscall_get_arguments(current, regs, args);
+	state->audit_syscall = syscall_get_nr(current, regs);
+	memcpy(state->audit_args, args, sizeof(state->audit_args));
+}
+
+static void pidfd_spawn_audit_entry(struct pidfd_spawn_state *state)
+{
+	audit_pidfd_spawn_entry(state->audit_syscall, state->audit_args[0],
+				state->audit_args[1], state->audit_args[2],
+				state->audit_args[3]);
+}
 static void pidfd_spawn_finish_child(struct pidfd_spawn_state *state,
 				     struct filename *filename, int result)
 {
@@ -391,6 +413,7 @@ static void pidfd_spawn_child(struct callback_head *work)
 	struct filename *filename;
 	int ret;
 
+	pidfd_spawn_audit_entry(state);
 	filename = complete_getname(&state->filename);
 	if (IS_ERR(filename))
 		ret = PTR_ERR(filename);
@@ -403,9 +426,11 @@ static void pidfd_spawn_child(struct callback_head *work)
 
 	pidfd_spawn_finish_child(state, filename, ret);
 	if (ret) {
+		audit_pidfd_spawn_exit(0, ret);
 		pidfd_spawn_state_put(state);
 		do_group_exit(PIDFD_SPAWN_EXIT_FAILURE);
 	}
+	audit_pidfd_spawn_exit(1, 0);
 	pidfd_spawn_state_put(state);
 }
 
@@ -575,6 +600,7 @@ static int pidfd_spawn_start(struct file *file,
 		state->argv = pidfd_spawn_user_arg(kargs->argv);
 		state->envp = pidfd_spawn_user_arg(kargs->envp);
 		pidfd_spawn_set_status(state, PIDFD_SPAWN_STARTING);
+		pidfd_spawn_save_audit_context(state);
 		reinit_completion(&state->done);
 
 		task = pidfd_spawn_create_task(file, state, &clone_args);
@@ -584,6 +610,9 @@ static int pidfd_spawn_start(struct file *file,
 			INIT_DELAYED_FILENAME(&state->filename);
 			state->argv = native_arg(NULL);
 			state->envp = native_arg(NULL);
+			memset(state->audit_args, 0,
+			       sizeof(state->audit_args));
+			state->audit_syscall = 0;
 			state->result = 0;
 			pidfd_spawn_set_status(state,
 					       PIDFD_SPAWN_CONFIGURING);
-- 
2.52.0