[PATCH 5.4 12/78] tpm: Handle negative priv->response_len in tpm_common_read()

[Greg Kroah-Hartman]

From: Tadeusz Struk <tadeusz.struk@xxxxxxxxx>

commit a430e67d9a2c62a8c7b315b99e74de02018d0a96 upstream.

The priv->response_length can hold the size of an response or an negative
error code, and the tpm_common_read() needs to handle both cases correctly.
Changed the type of response_length to signed and accounted for negative
value in tpm_common_read().

Cc: stable@xxxxxxxxxxxxxxx
Fixes: d23d12484307 ("tpm: fix invalid locking in NONBLOCKING mode")
Reported-by: Laura Abbott <labbott@xxxxxxxxxx>
Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxx>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/char/tpm/tpm-dev-common.c |    2 +-
 drivers/char/tpm/tpm-dev.h        |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -130,7 +130,7 @@ ssize_t tpm_common_read(struct file *fil
 		priv->response_read = true;
 
 		ret_size = min_t(ssize_t, size, priv->response_length);
-		if (!ret_size) {
+		if (ret_size <= 0) {
 			priv->response_length = 0;
 			goto out;
 		}
--- a/drivers/char/tpm/tpm-dev.h
+++ b/drivers/char/tpm/tpm-dev.h
@@ -14,7 +14,7 @@ struct file_priv {
 	struct work_struct timeout_work;
 	struct work_struct async_work;
 	wait_queue_head_t async_wait;
-	size_t response_length;
+	ssize_t response_length;
 	bool response_read;
 	bool command_enqueued;