selftests/bpf: Reject graph kptr use after RCU unlockgrafted

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 <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 306 insertions, 0 deletions

diff --git a/io_uring/fs.c b/io_uring/fs.c
new file mode 100644
index 000000000..26ea841a2
--- /dev/null
+++ b/io_uring/fs.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "../fs/internal.h"
+
+#include "io_uring.h"
+#include "fs.h"
+
+struct io_rename {
+	struct file			*file;
+	int				old_dfd;
+	int				new_dfd;
+	struct delayed_filename		oldpath;
+	struct delayed_filename		newpath;
+	int				flags;
+};
+
+struct io_unlink {
+	struct file			*file;
+	int				dfd;
+	int				flags;
+	struct delayed_filename		filename;
+};
+
+struct io_mkdir {
+	struct file			*file;
+	int				dfd;
+	umode_t				mode;
+	struct delayed_filename		filename;
+};
+
+struct io_link {
+	struct file			*file;
+	int				old_dfd;
+	int				new_dfd;
+	struct delayed_filename		oldpath;
+	struct delayed_filename		newpath;
+	int				flags;
+};
+
+int io_renameat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename);
+	const char __user *oldf, *newf;
+	int err;
+
+	if (sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	ren->old_dfd = READ_ONCE(sqe->fd);
+	oldf = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	newf = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+	ren->new_dfd = READ_ONCE(sqe->len);
+	ren->flags = READ_ONCE(sqe->rename_flags);
+
+	err = delayed_getname(&ren->oldpath, oldf);
+	if (unlikely(err))
+		return err;
+
+	err = delayed_getname(&ren->newpath, newf);
+	if (unlikely(err)) {
+		dismiss_delayed_filename(&ren->oldpath);
+		return err;
+	}
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_renameat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename);
+	CLASS(filename_complete_delayed, old)(&ren->oldpath);
+	CLASS(filename_complete_delayed, new)(&ren->newpath);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_renameat2(ren->old_dfd, old,
+				 ren->new_dfd, new, ren->flags);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_renameat_cleanup(struct io_kiocb *req)
+{
+	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename);
+
+	dismiss_delayed_filename(&ren->oldpath);
+	dismiss_delayed_filename(&ren->newpath);
+}
+
+int io_unlinkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_unlink *un = io_kiocb_to_cmd(req, struct io_unlink);
+	const char __user *fname;
+	int err;
+
+	if (sqe->off || sqe->len || sqe->buf_index || sqe->splice_fd_in ||
+	    sqe->addr3 || sqe->__pad2[0])
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	un->dfd = READ_ONCE(sqe->fd);
+
+	un->flags = READ_ONCE(sqe->unlink_flags);
+	if (un->flags & ~AT_REMOVEDIR)
+		return -EINVAL;
+
+	fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	err = delayed_getname(&un->filename, fname);
+	if (unlikely(err))
+		return err;
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_unlinkat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_unlink *un = io_kiocb_to_cmd(req, struct io_unlink);
+	CLASS(filename_complete_delayed, name)(&un->filename);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	if (un->flags & AT_REMOVEDIR)
+		ret = filename_rmdir(un->dfd, name);
+	else
+		ret = filename_unlinkat(un->dfd, name);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_unlinkat_cleanup(struct io_kiocb *req)
+{
+	struct io_unlink *ul = io_kiocb_to_cmd(req, struct io_unlink);
+
+	dismiss_delayed_filename(&ul->filename);
+}
+
+int io_mkdirat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_mkdir *mkd = io_kiocb_to_cmd(req, struct io_mkdir);
+	const char __user *fname;
+	int err;
+
+	if (sqe->off || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	mkd->dfd = READ_ONCE(sqe->fd);
+	mkd->mode = READ_ONCE(sqe->len);
+
+	fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	err = delayed_getname(&mkd->filename, fname);
+	if (unlikely(err))
+		return err;
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_mkdirat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_mkdir *mkd = io_kiocb_to_cmd(req, struct io_mkdir);
+	CLASS(filename_complete_delayed, name)(&mkd->filename);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_mkdirat(mkd->dfd, name, mkd->mode);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_mkdirat_cleanup(struct io_kiocb *req)
+{
+	struct io_mkdir *md = io_kiocb_to_cmd(req, struct io_mkdir);
+
+	dismiss_delayed_filename(&md->filename);
+}
+
+int io_symlinkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_link *sl = io_kiocb_to_cmd(req, struct io_link);
+	const char __user *oldpath, *newpath;
+	int err;
+
+	if (sqe->len || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	sl->new_dfd = READ_ONCE(sqe->fd);
+	oldpath = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	newpath = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+
+	err = delayed_getname(&sl->oldpath, oldpath);
+	if (unlikely(err))
+		return err;
+
+	err = delayed_getname(&sl->newpath, newpath);
+	if (unlikely(err)) {
+		dismiss_delayed_filename(&sl->oldpath);
+		return err;
+	}
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_symlinkat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_link *sl = io_kiocb_to_cmd(req, struct io_link);
+	CLASS(filename_complete_delayed, old)(&sl->oldpath);
+	CLASS(filename_complete_delayed, new)(&sl->newpath);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_symlinkat(old, sl->new_dfd, new);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+int io_linkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_link *lnk = io_kiocb_to_cmd(req, struct io_link);
+	const char __user *oldf, *newf;
+	int err;
+
+	if (sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	lnk->old_dfd = READ_ONCE(sqe->fd);
+	lnk->new_dfd = READ_ONCE(sqe->len);
+	oldf = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	newf = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+	lnk->flags = READ_ONCE(sqe->hardlink_flags);
+
+	err = delayed_getname_uflags(&lnk->oldpath, oldf, lnk->flags);
+	if (unlikely(err))
+		return err;
+
+	err = delayed_getname(&lnk->newpath, newf);
+	if (unlikely(err)) {
+		dismiss_delayed_filename(&lnk->oldpath);
+		return err;
+	}
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_linkat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_link *lnk = io_kiocb_to_cmd(req, struct io_link);
+	CLASS(filename_complete_delayed, old)(&lnk->oldpath);
+	CLASS(filename_complete_delayed, new)(&lnk->newpath);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_linkat(lnk->old_dfd, old, lnk->new_dfd, new, lnk->flags);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_link_cleanup(struct io_kiocb *req)
+{
+	struct io_link *sl = io_kiocb_to_cmd(req, struct io_link);
+
+	dismiss_delayed_filename(&sl->oldpath);
+	dismiss_delayed_filename(&sl->newpath);
+}