[PATCH 4.19 268/361] tpm: fix response size validation in tpm_get_random()

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>

commit 84b59f6487d82d3ab4247a099aba66d4d17e8b08 upstream.

When checking whether the response is large enough to be able to contain
the received random bytes in tpm_get_random() and tpm2_get_random(),
they fail to take account the header size, which should be added to the
minimum size. This commit fixes this issue.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: c659af78eb7b ("tpm: Check size of response before accessing data")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/char/tpm/tpm-interface.c |    3 ++-
 drivers/char/tpm/tpm2-cmd.c      |    4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -1322,7 +1322,8 @@ int tpm_get_random(struct tpm_chip *chip
 		}
 
 		rlength = be32_to_cpu(tpm_cmd.header.out.length);
-		if (rlength < offsetof(struct tpm_getrandom_out, rng_data) +
+		if (rlength < TPM_HEADER_SIZE +
+			      offsetof(struct tpm_getrandom_out, rng_data) +
 			      recd) {
 			total = -EFAULT;
 			break;
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -329,7 +329,9 @@ int tpm2_get_random(struct tpm_chip *chi
 			&buf.data[TPM_HEADER_SIZE];
 		recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
 		if (tpm_buf_length(&buf) <
-		    offsetof(struct tpm2_get_random_out, buffer) + recd) {
+		    TPM_HEADER_SIZE +
+		    offsetof(struct tpm2_get_random_out, buffer) +
+		    recd) {
 			err = -EFAULT;
 			goto out;
 		}