fanotify: support reporting thread id instead of process id

In order to identify which thread triggered the event in a
multi-threaded program, add the FAN_REPORT_TID flag in fanotify_init to
opt-in for reporting the event creator's thread id information.

Signed-off-by: nixiaoming <nixiaoming@huawei.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

5 files changed, 13 insertions, 6 deletions

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 361e3a0a445c..5769cf3ff035 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -25,7 +25,7 @@ static bool should_merge(struct fsnotify_event *old_fsn,
         old = FANOTIFY_E(old_fsn);
         new = FANOTIFY_E(new_fsn);
 
-        if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
+        if (old_fsn->inode == new_fsn->inode && old->pid == new->pid &&
             old->path.mnt == new->path.mnt &&
             old->path.dentry == new->path.dentry)
                 return true;
@@ -171,7 +171,10 @@ struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group,
                 goto out;
 init: __maybe_unused
         fsnotify_init_event(&event->fse, inode, mask);
-        event->tgid = get_pid(task_tgid(current));
+        if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
+                event->pid = get_pid(task_pid(current));
+        else
+                event->pid = get_pid(task_tgid(current));
         if (path) {
                 event->path = *path;
                 path_get(&event->path);
@@ -270,7 +273,7 @@ static void fanotify_free_event(struct fsnotify_event *fsn_event)
 
         event = FANOTIFY_E(fsn_event);
         path_put(&event->path);
-        put_pid(event->tgid);
+        put_pid(event->pid);
         if (fanotify_is_perm_event(fsn_event->mask)) {
                 kmem_cache_free(fanotify_perm_event_cachep,
                                 FANOTIFY_PE(fsn_event));
diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 88a8290a61cb..ea05b8a401e7 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -19,7 +19,7 @@ struct fanotify_event_info {
          * during this object's lifetime
          */
         struct path path;
-        struct pid *tgid;
+        struct pid *pid;
 };
 
 /*
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 14594e491d2b..e03be5071362 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -132,7 +132,7 @@ static int fill_event_metadata(struct fsnotify_group *group,
         metadata->vers = FANOTIFY_METADATA_VERSION;
         metadata->reserved = 0;
         metadata->mask = fsn_event->mask & FANOTIFY_OUTGOING_EVENTS;
-        metadata->pid = pid_vnr(event->tgid);
+        metadata->pid = pid_vnr(event->pid);
         if (unlikely(fsn_event->mask & FAN_Q_OVERFLOW))
                 metadata->fd = FAN_NOFD;
         else {
@@ -944,7 +944,7 @@ COMPAT_SYSCALL_DEFINE6(fanotify_mark,
  */
 static int __init fanotify_user_setup(void)
 {
-        BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 6);
+        BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 7);
         BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);
 
         fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index caf55c67fc6c..a5a60691e48b 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -19,6 +19,7 @@
                                  FAN_CLASS_PRE_CONTENT)
 
 #define FANOTIFY_INIT_FLAGS     (FANOTIFY_CLASS_BITS | \
+                                 FAN_REPORT_TID | \
                                  FAN_CLOEXEC | FAN_NONBLOCK | \
                                  FAN_UNLIMITED_QUEUE | FAN_UNLIMITED_MARKS)
 
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index d0c05de670ef..b86740d1c50a 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -40,6 +40,9 @@
 #define FAN_UNLIMITED_MARKS     0x00000020
 #define FAN_ENABLE_AUDIT        0x00000040
 
+/* Flags to determine fanotify event format */
+#define FAN_REPORT_TID          0x00000100      /* event->pid is thread id */
+
 /* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_INIT_FLAGS      (FAN_CLOEXEC | FAN_NONBLOCK | \
                                  FAN_ALL_CLASS_BITS | FAN_UNLIMITED_QUEUE |\