bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/io_uring/tctx.h b/io_uring/tctx.h
new file mode 100644
index 000000000..76ad1ad45
--- /dev/null
+++ b/io_uring/tctx.h
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+
+struct io_tctx_node {
+	struct list_head	ctx_node;
+	struct task_struct	*task;
+	struct io_ring_ctx	*ctx;
+};
+
+struct io_uring_task *io_uring_alloc_task_context(struct task_struct *task,
+						  struct io_ring_ctx *ctx);
+void io_uring_del_tctx_node(unsigned long index);
+int __io_uring_add_tctx_node(struct io_ring_ctx *ctx);
+int __io_uring_add_tctx_node_from_submit(struct io_ring_ctx *ctx);
+void io_uring_clean_tctx(struct io_uring_task *tctx);
+void io_uring_free_tctx(struct task_struct *tsk);
+
+void io_uring_unreg_ringfd(void);
+int io_ringfd_register(struct io_ring_ctx *ctx, void __user *__arg,
+		       unsigned nr_args);
+int io_ringfd_unregister(struct io_ring_ctx *ctx, void __user *__arg,
+			 unsigned nr_args);
+
+/*
+ * Note that this task has used io_uring. We use it for cancelation purposes.
+ */
+static inline int io_uring_add_tctx_node(struct io_ring_ctx *ctx)
+{
+	struct io_uring_task *tctx = current->io_uring;
+
+	if (likely(tctx && tctx->last == ctx))
+		return 0;
+
+	return __io_uring_add_tctx_node_from_submit(ctx);
+}