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, 246 insertions, 0 deletions

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
new file mode 100644
index 000000000..dc882fc9f
--- /dev/null
+++ b/drivers/char/tpm/tpm-buf.c
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Handling of TPM command and other buffers.
+ */
+
+#include <linux/tpm_command.h>
+#include <linux/module.h>
+#include <linux/tpm.h>
+
+/**
+ * tpm_buf_init() - Allocate and initialize a TPM command
+ * @buf:	A &tpm_buf
+ * @tag:	TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
+ * @ordinal:	A command ordinal
+ *
+ * Return: 0 or -ENOMEM
+ */
+int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
+	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
+	if (!buf->data)
+		return -ENOMEM;
+
+	tpm_buf_reset(buf, tag, ordinal);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_init);
+
+/**
+ * tpm_buf_reset() - Initialize a TPM command
+ * @buf:	A &tpm_buf
+ * @tag:	TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
+ * @ordinal:	A command ordinal
+ */
+void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+
+	WARN_ON(tag != TPM_TAG_RQU_COMMAND && tag != TPM2_ST_NO_SESSIONS &&
+		tag != TPM2_ST_SESSIONS && tag != 0);
+
+	buf->flags = 0;
+	buf->length = sizeof(*head);
+	head->tag = cpu_to_be16(tag);
+	head->length = cpu_to_be32(sizeof(*head));
+	head->ordinal = cpu_to_be32(ordinal);
+	buf->handles = 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_reset);
+
+/**
+ * tpm_buf_init_sized() - Allocate and initialize a sized (TPM2B) buffer
+ * @buf:	A @tpm_buf
+ *
+ * Return: 0 or -ENOMEM
+ */
+int tpm_buf_init_sized(struct tpm_buf *buf)
+{
+	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
+	if (!buf->data)
+		return -ENOMEM;
+
+	tpm_buf_reset_sized(buf);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_init_sized);
+
+/**
+ * tpm_buf_reset_sized() - Initialize a sized buffer
+ * @buf:	A &tpm_buf
+ */
+void tpm_buf_reset_sized(struct tpm_buf *buf)
+{
+	buf->flags = TPM_BUF_TPM2B;
+	buf->length = 2;
+	buf->data[0] = 0;
+	buf->data[1] = 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
+
+void tpm_buf_destroy(struct tpm_buf *buf)
+{
+	free_page((unsigned long)buf->data);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_destroy);
+
+/**
+ * tpm_buf_length() - Return the number of bytes consumed by the data
+ * @buf:	A &tpm_buf
+ *
+ * Return: The number of bytes consumed by the buffer
+ */
+u32 tpm_buf_length(struct tpm_buf *buf)
+{
+	return buf->length;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_length);
+
+/**
+ * tpm_buf_append() - Append data to an initialized buffer
+ * @buf:	A &tpm_buf
+ * @new_data:	A data blob
+ * @new_length:	Size of the appended data
+ */
+void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
+{
+	/* Return silently if overflow has already happened. */
+	if (buf->flags & TPM_BUF_OVERFLOW)
+		return;
+
+	if ((buf->length + new_length) > PAGE_SIZE) {
+		WARN(1, "tpm_buf: write overflow\n");
+		buf->flags |= TPM_BUF_OVERFLOW;
+		return;
+	}
+
+	memcpy(&buf->data[buf->length], new_data, new_length);
+	buf->length += new_length;
+
+	if (buf->flags & TPM_BUF_TPM2B)
+		((__be16 *)buf->data)[0] = cpu_to_be16(buf->length - 2);
+	else
+		((struct tpm_header *)buf->data)->length = cpu_to_be32(buf->length);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append);
+
+void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value)
+{
+	tpm_buf_append(buf, &value, 1);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u8);
+
+void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value)
+{
+	__be16 value2 = cpu_to_be16(value);
+
+	tpm_buf_append(buf, (u8 *)&value2, 2);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u16);
+
+void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
+{
+	__be32 value2 = cpu_to_be32(value);
+
+	tpm_buf_append(buf, (u8 *)&value2, 4);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
+
+/**
+ * tpm_buf_append_handle() - Add a handle
+ * @chip:	&tpm_chip instance
+ * @buf:	&tpm_buf instance
+ * @handle:	a TPM object handle
+ *
+ * Add a handle to the buffer, and increase the count tracking the number of
+ * handles in the command buffer. Works only for command buffers.
+ */
+void tpm_buf_append_handle(struct tpm_chip *chip, struct tpm_buf *buf, u32 handle)
+{
+	if (buf->flags & TPM_BUF_TPM2B) {
+		dev_err(&chip->dev, "Invalid buffer type (TPM2B)\n");
+		return;
+	}
+
+	tpm_buf_append_u32(buf, handle);
+	buf->handles++;
+}
+
+/**
+ * tpm_buf_read() - Read from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ * @count:	the number of bytes to read
+ * @output:	the output buffer
+ */
+static void tpm_buf_read(struct tpm_buf *buf, off_t *offset, size_t count, void *output)
+{
+	off_t next_offset;
+
+	/* Return silently if overflow has already happened. */
+	if (buf->flags & TPM_BUF_BOUNDARY_ERROR)
+		return;
+
+	next_offset = *offset + count;
+	if (next_offset > buf->length) {
+		WARN(1, "tpm_buf: read out of boundary\n");
+		buf->flags |= TPM_BUF_BOUNDARY_ERROR;
+		return;
+	}
+
+	memcpy(output, &buf->data[*offset], count);
+	*offset = next_offset;
+}
+
+/**
+ * tpm_buf_read_u8() - Read 8-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 8-bit word
+ */
+u8 tpm_buf_read_u8(struct tpm_buf *buf, off_t *offset)
+{
+	u8 value = 0;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return value;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u8);
+
+/**
+ * tpm_buf_read_u16() - Read 16-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 16-bit word
+ */
+u16 tpm_buf_read_u16(struct tpm_buf *buf, off_t *offset)
+{
+	u16 value = 0;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return be16_to_cpu(value);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u16);
+
+/**
+ * tpm_buf_read_u32() - Read 32-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 32-bit word
+ */
+u32 tpm_buf_read_u32(struct tpm_buf *buf, off_t *offset)
+{
+	u32 value = 0;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return be32_to_cpu(value);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u32);
+
+