From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- io_uring/epoll.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) create mode 100644 io_uring/epoll.c (limited to 'io_uring/epoll.c') diff --git a/io_uring/epoll.c b/io_uring/epoll.c new file mode 100644 index 000000000..b9db8bde2 --- /dev/null +++ b/io_uring/epoll.c @@ -0,0 +1,103 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "io_uring.h" +#include "epoll.h" + +struct io_epoll { + struct file *file; + int epfd; + int op; + int fd; + struct epoll_event event; +}; + +struct io_epoll_wait { + struct file *file; + int maxevents; + struct epoll_event __user *events; +}; + +int io_epoll_ctl_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_epoll *epoll = io_kiocb_to_cmd(req, struct io_epoll); + + if (sqe->buf_index || sqe->splice_fd_in) + return -EINVAL; + + epoll->epfd = READ_ONCE(sqe->fd); + epoll->op = READ_ONCE(sqe->len); + epoll->fd = READ_ONCE(sqe->off); + + if (ep_op_has_event(epoll->op)) { + struct epoll_event __user *ev; + + ev = u64_to_user_ptr(READ_ONCE(sqe->addr)); + if (copy_from_user(&epoll->event, ev, sizeof(*ev))) + return -EFAULT; + } + + return 0; +} + +int io_epoll_ctl(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_epoll *ie = io_kiocb_to_cmd(req, struct io_epoll); + bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK; + struct epoll_key key; + int ret; + + CLASS(fd, f)(ie->epfd); + if (fd_empty(f)) + return -EBADF; + + CLASS(fd, tf)(ie->fd); + if (fd_empty(tf)) + return -EBADF; + + key.file = fd_file(tf); + key.fd = ie->fd; + ret = do_epoll_ctl_file(fd_file(f), ie->op, &key, &ie->event, force_nonblock); + if (force_nonblock && ret == -EAGAIN) + return -EAGAIN; + + if (ret < 0) + req_set_fail(req); + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} + +int io_epoll_wait_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_epoll_wait *iew = io_kiocb_to_cmd(req, struct io_epoll_wait); + + if (sqe->off || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in) + return -EINVAL; + + iew->maxevents = READ_ONCE(sqe->len); + iew->events = u64_to_user_ptr(READ_ONCE(sqe->addr)); + return 0; +} + +int io_epoll_wait(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_epoll_wait *iew = io_kiocb_to_cmd(req, struct io_epoll_wait); + int ret; + + ret = epoll_sendevents(req->file, iew->events, iew->maxevents); + if (ret == 0) + return -EAGAIN; + if (ret < 0) + req_set_fail(req); + + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} -- cgit v1.3.1