[PATCH] tpm: infineon: add bounds check in tpm_inf_recv

[Shahriyar Jalayeri <shahriyar@posteo.de>]

Ensure tpm_inf_recv() does not overflow the provided buffer when
the TPM reports more data than the caller expects.

Signed-off-by: Shahriyar Jalayeri <shahriyar@posteo.de>
---
 drivers/char/tpm/tpm_infineon.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/char/tpm/tpm_infineon.c b/drivers/char/tpm/tpm_infineon.c
index 7638b65b8..eb6dd55ff 100644
--- a/drivers/char/tpm/tpm_infineon.c
+++ b/drivers/char/tpm/tpm_infineon.c
@@ -250,6 +250,12 @@ static int tpm_inf_recv(struct tpm_chip *chip, u8 * buf, size_t count)
 	number_of_wtx = 0;
 
 recv_begin:
+	if (count < 4) {
+		dev_err(&chip->dev,
+			"count less than the header size!\n");
+		return -EIO;
+	}
+
 	/* start receiving header */
 	for (i = 0; i < 4; i++) {
 		ret = wait(chip, STAT_RDA);
@@ -268,6 +274,12 @@ static int tpm_inf_recv(struct tpm_chip *chip, u8 * buf, size_t count)
 		/* size of the data received */
 		size = ((buf[2] << 8) | buf[3]);
 
+		if (size > count) {
+			dev_err(&chip->dev,
+				"Buffer too small for incoming data!\n");
+			return -EIO;
+		}
+
 		for (i = 0; i < size; i++) {
 			wait(chip, STAT_RDA);
 			buf[i] = tpm_data_in(RDFIFO);
-- 
2.43.0