On 3/4/20 12:02 PM, Josh Triplett wrote: > On Wed, Mar 04, 2020 at 11:00:16AM -0700, Jens Axboe wrote: >> sqe->len can be set to a specific fd we want to use for accept4(), so >> it uses that one instead of just assigning a free unused one. > [...] >> + accept->open_fd = READ_ONCE(sqe->len); >> + if (!accept->open_fd) >> + accept->open_fd = -1; > > 0 is a valid file descriptor. I realize that it seems unlikely, but I > went to a fair bit of trouble in my patch series to ensure that > userspace could use any valid file descriptor openat2, without a corner > case like "you can't open as file descriptor 0", even though it would > have been more convenient to just say "if you pass a non-zero fd in > open_how". Please consider accepting a flag to determine the validity of > open_fd. Heh, I actually just changed this, just added that as a temporary hack to verify that things were working. Now SOCK_SPECIFIC_FD is required, and we just gate on that. OP_ACCEPT disallowed fd != 0 before, so we continue to do that if SOCK_SPECIFIC_FD isn't set: https://git.kernel.dk/cgit/linux-block/log/?h=io_uring-fd-select top two patches. -- Jens Axboe
