Yesterday my 7 mo old vomated four times after eating more quantity as usual but today his poop was white with bad smell is there a problem or not?

There's a problem...: There is a problem, but the question is whether or not it's a big problem. Babies vomit and have poop changes with colds, stomach viruses, ear infections, throat infections, etc... If a baby otherwise looks fine and acts fine, and vomiting and poop changes only happen for a brief time (such as 6 hours), he may have a little problem that went away on its own. A doctor can evaluate to be certain.