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/truncate.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 io_uring/truncate.c (limited to 'io_uring/truncate.c') diff --git a/io_uring/truncate.c b/io_uring/truncate.c new file mode 100644 index 000000000..c88d8bd8d --- /dev/null +++ b/io_uring/truncate.c @@ -0,0 +1,48 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "../fs/internal.h" + +#include "io_uring.h" +#include "truncate.h" + +struct io_ftrunc { + struct file *file; + loff_t len; +}; + +int io_ftruncate_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_ftrunc *ft = io_kiocb_to_cmd(req, struct io_ftrunc); + + if (sqe->rw_flags || sqe->addr || sqe->len || sqe->buf_index || + sqe->splice_fd_in || sqe->addr3) + return -EINVAL; + + ft->len = READ_ONCE(sqe->off); + + req->flags |= REQ_F_FORCE_ASYNC; + return 0; +} + +int io_ftruncate(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_ftrunc *ft = io_kiocb_to_cmd(req, struct io_ftrunc); + int ret; + + WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK); + + ret = do_ftruncate(req->file, ft->len, 0); + + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} -- cgit v1.3.1