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, 66 insertions, 0 deletions

diff --git a/io_uring/filetable.h b/io_uring/filetable.h
new file mode 100644
index 000000000..c348233a3
--- /dev/null
+++ b/io_uring/filetable.h
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef IOU_FILE_TABLE_H
+#define IOU_FILE_TABLE_H
+
+#include <linux/io_uring_types.h>
+#include "rsrc.h"
+
+bool io_alloc_file_tables(struct io_ring_ctx *ctx, struct io_file_table *table, unsigned nr_files);
+void io_free_file_tables(struct io_ring_ctx *ctx, struct io_file_table *table);
+
+int io_fixed_fd_install(struct io_kiocb *req, unsigned int issue_flags,
+			struct file *file, unsigned int file_slot);
+int __io_fixed_fd_install(struct io_ring_ctx *ctx, struct file *file,
+				unsigned int file_slot);
+int io_fixed_fd_remove(struct io_ring_ctx *ctx, unsigned int offset);
+
+int io_register_file_alloc_range(struct io_ring_ctx *ctx,
+				 struct io_uring_file_index_range __user *arg);
+
+io_req_flags_t io_file_get_flags(struct file *file);
+
+static inline void io_file_bitmap_clear(struct io_file_table *table, int bit)
+{
+	WARN_ON_ONCE(!test_bit(bit, table->bitmap));
+	__clear_bit(bit, table->bitmap);
+	table->alloc_hint = bit;
+}
+
+static inline void io_file_bitmap_set(struct io_file_table *table, int bit)
+{
+	WARN_ON_ONCE(test_bit(bit, table->bitmap));
+	__set_bit(bit, table->bitmap);
+	table->alloc_hint = bit + 1;
+}
+
+#define FFS_NOWAIT		0x1UL
+#define FFS_ISREG		0x2UL
+#define FFS_MASK		~(FFS_NOWAIT|FFS_ISREG)
+
+static inline unsigned int io_slot_flags(struct io_rsrc_node *node)
+{
+
+	return (node->file_ptr & ~FFS_MASK) << REQ_F_SUPPORT_NOWAIT_BIT;
+}
+
+static inline struct file *io_slot_file(struct io_rsrc_node *node)
+{
+	return (struct file *)(node->file_ptr & FFS_MASK);
+}
+
+static inline void io_fixed_file_set(struct io_rsrc_node *node,
+				     struct file *file)
+{
+	node->file_ptr = (unsigned long)file |
+		(io_file_get_flags(file) >> REQ_F_SUPPORT_NOWAIT_BIT);
+}
+
+static inline void io_file_table_set_alloc_range(struct io_ring_ctx *ctx,
+						 unsigned off, unsigned len)
+{
+	ctx->file_alloc_start = off;
+	ctx->file_alloc_end = off + len;
+	ctx->file_table.alloc_hint = ctx->file_alloc_start;
+}
+
+#endif