Generally speaking (and I am sure someone will correct me if I'm wrong) when we refer to the "canon" we mean the following:
The Lord Of The Rings (all 3 volumes)
The Adventures Of Tom Bombadill
and maybe, The Children Of Hurin
Only 3 of those were written by JRRT exclusively; The Hobbit, The Lord Of The Rings, and The Adventures Of TB.
The Silmarillion was finished by Christopher Tolkien and we are not sure exactly what portions he authored. The notes left to him were apparently in quite a mess and he had to "adjust" some things in order to make the narrative consistent.
The Children Of Hurin is a compilation of various tales that JRRT wrote and these bits were done in various styles and Christopher put them together into a coherent novel (And I for one think he did a fine job).
The HOME books are compilations of JRRTs notes put together by Christopher.
"Just like Mary Shelly, Just like Frankenstein, Break your chains, And count your change, And try to walk the line"