If the TPM we're connecting to uses a static burst count, it will report
a burst count of zero throughout the response read. However, get_burstcount
assumes that a response of zero indicates that the TPM is not ready to
receive more data. In this case, it returns a negative error code, which
is passed on to tpm_tis_{write,read}_bytes as a u16, causing
them to read/write far too many bytes.
This patch checks for negative return codes and bails out from recv_data
and tpm_tis_send_data.
Fixes: 1107d065fdf1 (tpm_tis: Introduce intermediate layer for TPM access)
Signed-off-by: Josh Zimmerman <jo...@google.com>
---
Changelog v5:
- Move burstcnt < 0 check to before the min_t() call for enhanced readability.
Changelog v4:
- Add short description to Fixes tag line.
- Remove some unnecessary information in dev_err statements.
Changelog v3:
- Add signed-off-by.
Changelog v2:
- Fix typo (rc->burstcnt)
---
drivers/char/tpm/tpm_tis_core.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index e3bf31b..a1ce060 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -185,7 +185,12 @@ static int recv_data(struct tpm_chip *chip, u8 *buf,
size_t count)
TPM_STS_DATA_AVAIL | TPM_STS_VALID,
chip->timeout_c,
&priv->read_queue, true) == 0) {
- burstcnt = min_t(int, get_burstcount(chip), count - size);
+ burstcnt = get_burstcount(chip);
+ if (burstcnt < 0) {
+ dev_err(&chip->dev, "Unable to read burstcount\n");
+ return burstcnt;
+ }
+ burstcnt = min_t(int, burstcnt, count - size);
rc = tpm_tis_read_bytes(priv, TPM_DATA_FIFO(priv->locality),
burstcnt, buf + size);
@@ -271,7 +276,13 @@ static int tpm_tis_send_data(struct tpm_chip *chip, u8
*buf, size_t len)
}
while (count < len - 1) {
- burstcnt = min_t(int, get_burstcount(chip), len - count - 1);
+ burstcnt = get_burstcount(chip);
+ if (burstcnt < 0) {
+ dev_err(&chip->dev, "Unable to read burstcount\n");
+ rc = burstcnt;
+ goto out_err;
+ }
+ burstcnt = min_t(int, burstcnt, len - count - 1);
rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality),
burstcnt, buf + count);
if (rc < 0)
--
2.8.0.rc3.226.g39d4020
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