[PATCH 5.10 003/663] debugfs: be more robust at handling improper input in debugfs_lookup()

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

commit bc6de804d36b3709d54fa22bd128cbac91c11526 upstream.

debugfs_lookup() doesn't like it if it is passed an illegal name
pointer, or if the filesystem isn't even initialized yet.  If either of
these happen, it will crash the system, so fix it up by properly testing
for valid input and that we are up and running before trying to find a
file in the filesystem.

Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Reported-by: Michael Walle <michael@xxxxxxxx>
Tested-by: Michael Walle <michael@xxxxxxxx>
Tested-by: Marc Zyngier <maz@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210218100818.3622317-1-gregkh@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/debugfs/inode.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -297,7 +297,7 @@ struct dentry *debugfs_lookup(const char
 {
 	struct dentry *dentry;
 
-	if (IS_ERR(parent))
+	if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
 		return NULL;
 
 	if (!parent)