Merge tag 'fsnotify_for_v7.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull fsnotify updates from Jan Kara:

 - fanotify improvements for pidfd reporting

 - small cleanup in fanotify_error_event_equal

* tag 'fsnotify_for_v7.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fanotify: allow reporting pidfds for reaped tasks
  fanotify: report thread pidfds for FAN_REPORT_TID
  fanotify: simplify fanotify_error_event_equal

Author: torvalds

fs/notify/fanotify/fanotify.c

@@ -14,6 +14,7 @@
 #include <linux/sched/mm.h>
 #include <linux/statfs.h>
 #include <linux/stringhash.h>
+#include <linux/pidfs.h>
 
 #include "fanotify.h"
 
@@ -120,10 +121,7 @@ static bool fanotify_error_event_equal(struct fanotify_error_event *fee1,
 				       struct fanotify_error_event *fee2)
 {
 	/* Error events against the same file system are always merged. */
-	if (!fanotify_fsid_equal(&fee1->fsid, &fee2->fsid))
-		return false;
-
-	return true;
+	return fanotify_fsid_equal(&fee1->fsid, &fee2->fsid);
 }
 
 static bool fanotify_should_merge(struct fanotify_event *old,
@@ -842,6 +840,15 @@ static struct fanotify_event *fanotify_alloc_event(
 	/* Whoever is interested in the event, pays for the allocation. */
 	old_memcg = set_active_memcg(group->memcg);
 
+	if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
+		pid = task_pid(current);
+	else
+		pid = task_tgid(current);
+
+	if (FAN_GROUP_FLAG(group, FAN_REPORT_PIDFD) &&
+	    pidfs_register_pid_gfp(pid, gfp))
+		goto out;
+
 	if (fanotify_is_perm_event(mask)) {
 		event = fanotify_alloc_perm_event(data, data_type, gfp);
 	} else if (fanotify_is_error_event(mask)) {
@@ -863,15 +870,10 @@ static struct fanotify_event *fanotify_alloc_event(
 	if (!event)
 		goto out;
 
-	if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
-		pid = get_pid(task_pid(current));
-	else
-		pid = get_pid(task_tgid(current));
-
 	/* Mix event info, FAN_ONDIR flag and pid into event merge key */
 	hash ^= hash_long((unsigned long)pid | ondir, FANOTIFY_EVENT_HASH_BITS);
 	fanotify_init_event(event, hash, mask);
-	event->pid = pid;
+	event->pid = get_pid(pid);
 
 out:
 	set_active_memcg(old_memcg);

fs/notify/fanotify/fanotify_user.c

@@ -19,6 +19,7 @@
 #include <linux/memcontrol.h>
 #include <linux/statfs.h>
 #include <linux/exportfs.h>
+#include <linux/pidfd.h>
 
 #include <asm/ioctls.h>
 
@@ -903,25 +904,13 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 		metadata.fd = fd >= 0 ? fd : FAN_NOFD;
 
 	if (pidfd_mode) {
-		/*
-		 * Complain if the FAN_REPORT_PIDFD and FAN_REPORT_TID mutual
-		 * exclusion is ever lifted. At the time of incoporating pidfd
-		 * support within fanotify, the pidfd API only supported the
-		 * creation of pidfds for thread-group leaders.
-		 */
-		WARN_ON_ONCE(FAN_GROUP_FLAG(group, FAN_REPORT_TID));
+		unsigned int pidfd_flags = PIDFD_STALE;
 
-		/*
-		 * The PIDTYPE_TGID check for an event->pid is performed
-		 * preemptively in an attempt to catch out cases where the event
-		 * listener reads events after the event generating process has
-		 * already terminated.  Depending on flag FAN_REPORT_FD_ERROR,
-		 * report either -ESRCH or FAN_NOPIDFD to the event listener in
-		 * those cases with all other pidfd creation errors reported as
-		 * the error code itself or as FAN_EPIDFD.
-		 */
-		if (metadata.pid && pid_has_task(event->pid, PIDTYPE_TGID))
-			pidfd = pidfd_prepare(event->pid, 0, &pidfd_file);
+		if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
+			pidfd_flags |= PIDFD_THREAD;
+
+		if (metadata.pid)
+			pidfd = pidfd_prepare(event->pid, pidfd_flags, &pidfd_file);
 
 		if (!FAN_GROUP_FLAG(group, FAN_REPORT_FD_ERROR) && pidfd < 0)
 			pidfd = pidfd == -ESRCH ? FAN_NOPIDFD : FAN_EPIDFD;
@@ -1628,14 +1617,6 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 #endif
 		return -EINVAL;
 
-	/*
-	 * A pidfd can only be returned for a thread-group leader; thus
-	 * FAN_REPORT_PIDFD and FAN_REPORT_TID need to remain mutually
-	 * exclusive.
-	 */
-	if ((flags & FAN_REPORT_PIDFD) && (flags & FAN_REPORT_TID))
-		return -EINVAL;
-
 	/* Don't allow mixing mnt events with inode events for now */
 	if (flags & FAN_REPORT_MNT) {
 		if (class != FAN_CLASS_NOTIF)

fs/pidfs.c

@@ -977,14 +977,16 @@ static void pidfs_put_data(void *data)
 }
 
 /**
- * pidfs_register_pid - register a struct pid in pidfs
+ * pidfs_register_pid_gfp - register a struct pid in pidfs with custom GFP
+ * flags
  * @pid: pid to pin
+ * @gfp: GFP flags for memory allocation
  *
- * Register a struct pid in pidfs.
+ * Register a struct pid in pidfs with custom GFP flags.
  *
  * Return: On success zero, on error a negative error code is returned.
  */
-int pidfs_register_pid(struct pid *pid)
+int pidfs_register_pid_gfp(struct pid *pid, gfp_t gfp)
 {
 	struct pidfs_attr *new_attr __free(kfree) = NULL;
 	struct pidfs_attr *attr;
@@ -1000,7 +1002,7 @@ int pidfs_register_pid(struct pid *pid)
 	if (attr)
 		return 0;
 
-	new_attr = kmem_cache_zalloc(pidfs_attr_cachep, GFP_KERNEL);
+	new_attr = kmem_cache_zalloc(pidfs_attr_cachep, gfp);
 	if (!new_attr)
 		return -ENOMEM;
 

include/linux/pidfs.h

@@ -2,6 +2,8 @@
 #ifndef _LINUX_PID_FS_H
 #define _LINUX_PID_FS_H
 
+#include <linux/gfp_types.h>
+
 struct coredump_params;
 
 struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags);
@@ -14,7 +16,21 @@ void pidfs_exit(struct task_struct *tsk);
 void pidfs_coredump(const struct coredump_params *cprm);
 #endif
 extern const struct dentry_operations pidfs_dentry_operations;
-int pidfs_register_pid(struct pid *pid);
+int pidfs_register_pid_gfp(struct pid *pid, gfp_t gfp);
+
+/**
+ * pidfs_register_pid - register a struct pid in pidfs
+ * @pid: pid to pin
+ *
+ * Register a struct pid in pidfs.
+ *
+ * Return: On success zero, on error a negative error code is returned.
+ */
+static inline int pidfs_register_pid(struct pid *pid)
+{
+	return pidfs_register_pid_gfp(pid, GFP_KERNEL);
+}
+
 void pidfs_free_pid(struct pid *pid);
 
 #endif /* _LINUX_PID_FS_H */