debugfs can now report an error code if something went wrong instead of
just NULL. So if the return value is to be used as a "real" dentry, it
needs to be checked if it is an error before dereferencing it.
This is now happening because of ff9fb72b ("debugfs: return error
values, not NULL"). syzbot has found a way to trigger multiple debugfs
files attempting to be created, which fails, and then the error code
gets passed to dentry_path_raw() which obviously does not like it.
Reported-by: Eric Biggers <email@example.com>
Cc: "Radim Krčmář" <firstname.lastname@example.org>
Acked-by: Paolo Bonzini <email@example.com>
Signed-off-by: Greg Kroah-Hartman <firstname.lastname@example.org>
Signed-off-by: Linus Torvalds <email@example.com>