eventfs: Fix events beyond NAME_MAX blocking tasks

Eventfs uses simple_lookup(), however, it will fail if the name of the
entry is beyond NAME_MAX length. When this error is encountered, eventfs
still tries to create dentries instead of skipping the dentry creation.
When the dentry is attempted to be created in this state d_wait_lookup()
will loop forever, waiting for the lookup to be removed.

Fix eventfs to return the error in simple_lookup() back to the caller
instead of continuing to try to create the dentry.

Link: https://lore.kernel.org/linux-trace-kernel/20231210213534.497-1-beaub@linux.microsoft.com
Fixes: 63940449555e ("eventfs: Implement eventfs lookup, read, open functions")
Link: https://lore.kernel.org/linux-trace-kernel/20231208183601.GA46-beaub@linux.microsoft.com/
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 0b90869..43e2378 100644 (file)
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -546,6 +546,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
                if (strcmp(ei_child->name, name) != 0)
                        continue;
                ret = simple_lookup(dir, dentry, flags);
+               if (IS_ERR(ret))
+                       goto out;
                create_dir_dentry(ei, ei_child, ei_dentry, true);
                created = true;
                break;
@@ -568,6 +570,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
                        if (r <= 0)
                                continue;
                        ret = simple_lookup(dir, dentry, flags);
+                       if (IS_ERR(ret))
+                               goto out;
                        create_file_dentry(ei, i, ei_dentry, name, mode, cdata,
                                           fops, true);
                        break;