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, 54 insertions, 0 deletions

diff --git a/drivers/char/tpm/tpmrm-dev.c b/drivers/char/tpm/tpmrm-dev.c
new file mode 100644
index 000000000..19e8f2779
--- /dev/null
+++ b/drivers/char/tpm/tpmrm-dev.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2017 James.Bottomley@HansenPartnership.com
+ */
+#include <linux/slab.h>
+#include "tpm-dev.h"
+
+struct tpmrm_priv {
+	struct file_priv priv;
+	struct tpm_space space;
+};
+
+static int tpmrm_open(struct inode *inode, struct file *file)
+{
+	struct tpm_chip *chip;
+	struct tpmrm_priv *priv;
+	int rc;
+
+	chip = container_of(inode->i_cdev, struct tpm_chip, cdevs);
+	priv = kzalloc_obj(*priv);
+	if (priv == NULL)
+		return -ENOMEM;
+
+	rc = tpm2_init_space(&priv->space, TPM2_SPACE_BUFFER_SIZE);
+	if (rc) {
+		kfree(priv);
+		return -ENOMEM;
+	}
+
+	tpm_common_open(file, chip, &priv->priv, &priv->space);
+
+	return nonseekable_open(inode, file);
+}
+
+static int tpmrm_release(struct inode *inode, struct file *file)
+{
+	struct file_priv *fpriv = file->private_data;
+	struct tpmrm_priv *priv = container_of(fpriv, struct tpmrm_priv, priv);
+
+	tpm_common_release(file, fpriv);
+	tpm2_del_space(fpriv->chip, &priv->space);
+	kfree(priv);
+
+	return 0;
+}
+
+const struct file_operations tpmrm_fops = {
+	.owner = THIS_MODULE,
+	.open = tpmrm_open,
+	.read = tpm_common_read,
+	.write = tpm_common_write,
+	.poll = tpm_common_poll,
+	.release = tpmrm_release,
+};