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, 26 insertions, 0 deletions

diff --git a/drivers/md/dm-vdo/permassert.c b/drivers/md/dm-vdo/permassert.c
new file mode 100644
index 000000000..bf9eccea1
--- /dev/null
+++ b/drivers/md/dm-vdo/permassert.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "permassert.h"
+
+#include "errors.h"
+#include "logger.h"
+
+int vdo_assertion_failed(const char *expression_string, const char *file_name,
+			 int line_number, const char *format, ...)
+{
+	va_list args;
+
+	va_start(args, format);
+
+	vdo_log_embedded_message(VDO_LOG_ERR, VDO_LOGGING_MODULE_NAME, "assertion \"",
+				 format, args, "\" (%s) failed at %s:%d",
+				 expression_string, file_name, line_number);
+	vdo_log_backtrace(VDO_LOG_ERR);
+
+	va_end(args);
+
+	return UDS_ASSERTION_FAILED;
+}