[PATCH] tpm: Check return value of crypto_kpp_set_secret()

[Eric Biggers <ebiggers@kernel.org>]

crypto_kpp_set_secret() can fail, for example if the kernel is booted
with fips=1 and the broken-by-design FIPS RNG used for ECC private key
generation doesn't feel like generating random bytes at the moment.
Check for error, cancelling the TPM session creation rather than
proceeding with a zero or uninitialized private key.

Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 drivers/char/tpm/tpm2-sessions.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index ca1e2bf424e14..2aaaad69760dc 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -527,7 +527,9 @@ static int tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip,
 	}
 	crypto_ecdh_encode_key(encoded_key, buf_len, &p);
 	/* this generates a random private key */
-	crypto_kpp_set_secret(kpp, encoded_key, buf_len);
+	rc = crypto_kpp_set_secret(kpp, encoded_key, buf_len);
+	if (rc)
+		goto err_free_kpp;
 
 	/* salt is now the public point of this private key */
 	req = kpp_request_alloc(kpp, GFP_KERNEL);

base-commit: 21a7f44fd0765fcc5194130b28767786eba1d1e7
-- 
2.56.0