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, 57 insertions, 0 deletions

diff --git a/io_uring/notif.h b/io_uring/notif.h
new file mode 100644
index 000000000..f3589cfef
--- /dev/null
+++ b/io_uring/notif.h
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/net.h>
+#include <linux/uio.h>
+#include <net/sock.h>
+#include <linux/nospec.h>
+
+#include "rsrc.h"
+
+#define IO_NOTIF_UBUF_FLAGS	(SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN)
+#define IO_NOTIF_SPLICE_BATCH	32
+
+struct io_notif_data {
+	struct file		*file;
+	struct ubuf_info	uarg;
+
+	struct io_notif_data	*next;
+	struct io_notif_data	*head;
+
+	unsigned		account_pages;
+	bool			zc_report;
+	bool			zc_used;
+	bool			zc_copied;
+};
+
+struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx);
+void io_tx_ubuf_complete(struct sk_buff *skb, struct ubuf_info *uarg,
+			 bool success);
+
+static inline struct io_notif_data *io_notif_to_data(struct io_kiocb *notif)
+{
+	return io_kiocb_to_cmd(notif, struct io_notif_data);
+}
+
+static inline void io_notif_flush(struct io_kiocb *notif)
+	__must_hold(&notif->ctx->uring_lock)
+{
+	struct io_notif_data *nd = io_notif_to_data(notif);
+
+	io_tx_ubuf_complete(NULL, &nd->uarg, true);
+}
+
+static inline int io_notif_account_mem(struct io_kiocb *notif, unsigned len)
+{
+	struct io_ring_ctx *ctx = notif->ctx;
+	struct io_notif_data *nd = io_notif_to_data(notif);
+	unsigned nr_pages = (len >> PAGE_SHIFT) + 2;
+	int ret;
+
+	if (ctx->user) {
+		ret = __io_account_mem(ctx->user, nr_pages);
+		if (ret)
+			return ret;
+		nd->account_pages += nr_pages;
+	}
+	return 0;
+}