linux-kernel - [PATCH v2 7/9] tpm-buf: check for corruption in tpm_buf_append

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Message-Id: <20250929035938.1773341-8-jarkko@kernel.org>
Date: Mon, 29 Sep 2025 06:59:36 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: linux-integrity@...r.kernel.org
Cc: dpsmith@...rtussolutions.com,
	ross.philipson@...cle.com,
	Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>,
	Peter Huewe <peterhuewe@....de>,
	Jarkko Sakkinen <jarkko@...nel.org>,
	Jason Gunthorpe <jgg@...pe.ca>,
	David Howells <dhowells@...hat.com>,
	Paul Moore <paul@...l-moore.com>,
	James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Mimi Zohar <zohar@...ux.ibm.com>,
	linux-kernel@...r.kernel.org (open list),
	keyrings@...r.kernel.org (open list:KEYS/KEYRINGS),
	linux-security-module@...r.kernel.org (open list:SECURITY SUBSYSTEM)
Subject: [PATCH v2 7/9] tpm-buf: check for corruption in  tpm_buf_append_handle()

From: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>

Unify TPM_BUF_BOUNDARY_ERROR and TPM_BUF_OVERFLOW into TPM_BUF_INVALID
flag because semantically they are identical.

Test and set TPM_BUF_INVALID in tpm_buf_append_handle() following the
pattern from other functions in tpm-buf.c.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>
---
v2:
- A new patch.
---
 drivers/char/tpm/tpm-buf.c                | 14 ++++++++------
 include/linux/tpm.h                       |  8 +++-----
 security/keys/trusted-keys/trusted_tpm2.c |  6 +++---
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index dc882fc9fa9e..5526f548b4de 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -104,13 +104,12 @@ EXPORT_SYMBOL_GPL(tpm_buf_length);
  */
 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)
+	if (buf->flags & TPM_BUF_INVALID)
 		return;
 
 	if ((buf->length + new_length) > PAGE_SIZE) {
 		WARN(1, "tpm_buf: write overflow\n");
-		buf->flags |= TPM_BUF_OVERFLOW;
+		buf->flags |= TPM_BUF_INVALID;
 		return;
 	}
 
@@ -157,7 +156,11 @@ EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
  */
 void tpm_buf_append_handle(struct tpm_chip *chip, struct tpm_buf *buf, u32 handle)
 {
+	if (buf->flags & TPM_BUF_INVALID)
+		return;
+
 	if (buf->flags & TPM_BUF_TPM2B) {
+		buf->flags |= TPM_BUF_INVALID;
 		dev_err(&chip->dev, "Invalid buffer type (TPM2B)\n");
 		return;
 	}
@@ -177,14 +180,13 @@ static void tpm_buf_read(struct tpm_buf *buf, off_t *offset, size_t count, void
 {
 	off_t next_offset;
 
-	/* Return silently if overflow has already happened. */
-	if (buf->flags & TPM_BUF_BOUNDARY_ERROR)
+	if (buf->flags & TPM_BUF_INVALID)
 		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;
+		buf->flags |= TPM_BUF_INVALID;
 		return;
 	}
 
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index e72e7657faa2..5283f32781c4 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -366,12 +366,10 @@ struct tpm_header {
 } __packed;
 
 enum tpm_buf_flags {
-	/* the capacity exceeded: */
-	TPM_BUF_OVERFLOW	= BIT(0),
 	/* TPM2B format: */
-	TPM_BUF_TPM2B		= BIT(1),
-	/* read out of boundary: */
-	TPM_BUF_BOUNDARY_ERROR	= BIT(2),
+	TPM_BUF_TPM2B		= BIT(0),
+	/* The buffer is in invalid and unusable state: */
+	TPM_BUF_INVALID		= BIT(1),
 };
 
 /*
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index 8e3b283a59b2..119d5152c0db 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -295,7 +295,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	/* creation PCR */
 	tpm_buf_append_u32(&buf, 0);
 
-	if (buf.flags & TPM_BUF_OVERFLOW) {
+	if (buf.flags & TPM_BUF_INVALID) {
 		rc = -E2BIG;
 		tpm2_end_auth_session(chip);
 		goto out;
@@ -308,7 +308,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		goto out;
 
 	blob_len = tpm_buf_read_u32(&buf, &offset);
-	if (blob_len > MAX_BLOB_SIZE || buf.flags & TPM_BUF_BOUNDARY_ERROR) {
+	if (blob_len > MAX_BLOB_SIZE || buf.flags & TPM_BUF_INVALID) {
 		rc = -E2BIG;
 		goto out;
 	}
@@ -414,7 +414,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 
 	tpm_buf_append(&buf, blob, blob_len);
 
-	if (buf.flags & TPM_BUF_OVERFLOW) {
+	if (buf.flags & TPM_BUF_INVALID) {
 		rc = -E2BIG;
 		tpm2_end_auth_session(chip);
 		goto out;
-- 
2.39.5