Coldplay -- The Amy Winehouse Tribute

Coldplay honored the memory of Amy Winehouse with a moving rendition of "Rehab" during their show at the Samsung AT&T Summer Krush concert -- while a TON of stars watched in the crowd.

Lindsay Lohan, Gwyneth Paltrow, Channing Tatum, Kate Bosworth and Heidi Klum were all at UCLA to check out the show.

So to summarize -- Coldplay played "Rehab" in front of Lindsay Lohan ... who once went to rehab at UCLA.