[PATCH] tpm: Fix heap buffer overflow in tpm_transmit_cmd()

[Jiangshan Yi]

struct tpm_buf now uses an embedded flexible array for data, which is
6 bytes shorter than TPM_BUFSIZE due to the struct header. But
tpm_transmit_cmd() still passes PAGE_SIZE to tpm_transmit(), and after
clamping to TPM_BUFSIZE in tpm_try_transmit(), chip->ops->recv() can
write past the end of data[] by 6 bytes.

Pass buf->capacity to tpm_transmit() instead.

Fixes: 3d9e043dab0a ("tpm-buf: Memory-safe allocations")
Cc: sta...@vger.kernel.org
Signed-off-by: Jiangshan Yi <yijiangs...@kylinos.cn>
---
 drivers/char/tpm/tpm-interface.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index f745a098908b..1ccdbde98b69 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -268,7 +268,7 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct 
tpm_buf *buf,
        int err;
        ssize_t len;
 
-       len = tpm_transmit(chip, buf->data, PAGE_SIZE);
+       len = tpm_transmit(chip, buf->data, buf->capacity);
        if (len <  0)
                return len;
 
-- 
2.25.1