tracefs: Zero out the tracefs_inode when allocating it

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 to access to ti->private. The assignment still needs
to be made before the dentry is instantiated.

Link: https://lore.kernel.org/linux-trace-kernel/20240131185512.315825944@goodmis.org
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Ajay Kaher <ajay.kaher@broadcom.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202401291043.e62e89dc-oliver.sang@intel.com
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index e1b172c0e091a8d55fcc80951fa4ed5202b1539e..888e4208784777dd7125b6b7bd5a2205765ba72c 100644 (file)
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -38,8 +38,6 @@ static struct inode *tracefs_alloc_inode(struct super_block *sb)
        if (!ti)
                return NULL;
 
-       ti->flags = 0;
-
        return &ti->vfs_inode;
 }
 
@@ -779,7 +777,11 @@ static void init_once(void *foo)
 {
        struct tracefs_inode *ti = (struct tracefs_inode *) foo;
 
+       /* inode_init_once() calls memset() on the vfs_inode portion */
        inode_init_once(&ti->vfs_inode);
+
+       /* Zero out the rest */
+       memset_after(ti, 0, vfs_inode);
 }
 
 static int __init tracefs_init(void)

diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h
index 91c2bf0b91d9c53d83b6325161787b090f2ba574..7d84349ade87227b3e1eca62a9393f7ab2979383 100644 (file)
--- a/fs/tracefs/internal.h
+++ b/fs/tracefs/internal.h
@@ -11,9 +11,10 @@ enum {
 };
 
 struct tracefs_inode {
+       struct inode            vfs_inode;
+       /* The below gets initialized with memset_after(ti, 0, vfs_inode) */
        unsigned long           flags;
        void                    *private;
-       struct inode            vfs_inode;
 };
 
 /*