linux-kernel - [PATCH] tracefs: Zero out the tracefs

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Date: Tue, 30 Jan 2024 15:17:37 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Christian Brauner <brauner@...nel.org>, Al Viro <viro@...IV.linux.org.uk>
Subject: [PATCH] tracefs: Zero out the tracefs_inode when allocating it

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

eventfs uses the tracefs_inode and assumes that it's already initialized
to zero. That is, it doesn't set fields to zero (like ti->private) after
getting its tracefs_inode. This causes bugs due to stale values.

Just initialize the entire structure to zero on allocation so there isn't
any more surprises.

This is a partial fix for accessing ti->private. The assignment still needs
to be made before the dentry is instantiated.

Cc: stable@...r.kernel.org
Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode")
Reported-by: kernel test robot <oliver.sang@...el.com>
Closes: https://lore.kernel.org/oe-lkp/202401291043.e62e89dc-oliver.sang@intel.com
Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 fs/tracefs/inode.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index e1b172c0e091..f7cde61ff2fc 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -34,12 +34,10 @@ static struct inode *tracefs_alloc_inode(struct super_block *sb)
 {
 	struct tracefs_inode *ti;
 
-	ti = kmem_cache_alloc(tracefs_inode_cachep, GFP_KERNEL);
+	ti = kmem_cache_alloc(tracefs_inode_cachep, GFP_KERNEL | __GFP_ZERO);
 	if (!ti)
 		return NULL;
 
-	ti->flags = 0;
-
 	return &ti->vfs_inode;
 }
 
-- 
2.43.0