On Thu, 09 Feb 2023 12:13:05 +0000 Pietro Borrello wrote: > The list_entry on an empty list creates a type confused pointer. > While using it is undefined behavior, in this case it seems there > is no big risk, as the `tsp->asoc != assoc` check will almost > certainly fail on the type confused pointer. > We report this bug also since it may hide further problems since > the code seems to assume a non-empty `ep->asocs`. > > We were able to trigger sctp_sock_filter() using syzkaller, and > cause a panic inserting `BUG_ON(list_empty(&ep->asocs))`, so the > list may actually be empty. > But we were not able to minimize our testcase and understand how > sctp_sock_filter may end up with an empty asocs list. > We suspect a race condition between a connecting sctp socket > and the diag query. > > We attach the stacktrace when triggering the injected > `BUG_ON(list_empty(&ep->asocs))`: Thanks for the analysis, but I'll put this in for 6.2 anyway. The patch looks fairly straightforward / provably correct, and with the Fixes tag present chances are it will end up in stable either way. With a difference of maybe a week, since the merge window is just a week away..