[for-next][PATCH 01/11] eventfs: Add WARN_ON_ONCE() to checks in eventfs_root_lookup()

Steven Rostedt
2024-02-21T14:06:40Z

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

There's a couple of if statements in eventfs_root_lookup() that should
never be true. Instead of removing them, add WARN_ON_ONCE() around them.

One is a tracefs_inode not being for eventfs.

The other is a child being freed but still on the parent's children
list. When a child is freed, it is removed from the list under the
same mutex that is held during the iteration.

Link: https://lore.kernel.org/linux-trace-kernel/20240201002719.GS2087318@ZenIV/
Link: https://lore.kernel.org/linux-trace-kernel/20240201123346.724afa46@gandalf.local.home

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ajay Kaher <ajay.kaher@broadcom.com>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
fs/tracefs/event_inode.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 110e8a272189..9d9c7dc3114b 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -483,7 +483,7 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
struct dentry *result = NULL;

ti = get_tracefs(dir);
- if (!(ti->flags & TRACEFS_EVENT_INODE))
+ if (WARN_ON_ONCE(!(ti->flags & TRACEFS_EVENT_INODE)))
return ERR_PTR(-EIO);

mutex_lock(&eventfs_mutex);
@@ -495,7 +495,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
list_for_each_entry(ei_child, &ei->children, list) {
if (strcmp(ei_child->name, name) != 0)
continue;
- if (ei_child->is_freed)
+ /* A child is freed and removed from the list at the same time */
+ if (WARN_ON_ONCE(ei_child->is_freed))
goto out;
result = lookup_dir_entry(dentry, ei, ei_child);
goto out;
--
2.43.0