[PATCH] tpm: fail tpm_validate_command() if chip->nr_commands is zero

[Jarkko Sakkinen]

Now that tpm_validate_command() is only on TPM2 space code path, it
should return -EINVAL in the case nr_command is zero, as it should never
be. Not doing this could cause cc to be uninitialized. This commit fixes
the issue.

Fixes: a4bfd02c6b00 ("tpm: move tpm_validate_commmand() to tpm2-space.c")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
---
 drivers/char/tpm/tpm2-space.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index a9ced49546ad..4a2773c3374f 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -263,8 +263,9 @@ static int tpm2_map_command(struct tpm_chip *chip, u32 cc, u8 *cmd)
 	return 0;
 }
 
-static int tpm_validate_command(struct tpm_chip *chip, struct tpm_space *space,
-				const void *cmd, size_t len)
+static int tpm_find_and_validate_cc(struct tpm_chip *chip,
+				    struct tpm_space *space,
+				    const void *cmd, size_t len)
 {
 	const struct tpm_header *header = (const void *)cmd;
 	int i;
@@ -272,26 +273,24 @@ static int tpm_validate_command(struct tpm_chip *chip, struct tpm_space *space,
 	u32 attrs;
 	unsigned int nr_handles;
 
-	if (len < TPM_HEADER_SIZE)
+	if (len < TPM_HEADER_SIZE || !chip->nr_commands)
 		return -EINVAL;
 
-	if (chip->nr_commands) {
-		cc = be32_to_cpu(header->ordinal);
+	cc = be32_to_cpu(header->ordinal);
 
-		i = tpm2_find_cc(chip, cc);
-		if (i < 0) {
-			dev_dbg(&chip->dev, "0x%04X is an invalid command\n",
-				cc);
-			return -EOPNOTSUPP;
-		}
-
-		attrs = chip->cc_attrs_tbl[i];
-		nr_handles =
-			4 * ((attrs >> TPM2_CC_ATTR_CHANDLES) & GENMASK(2, 0));
-		if (len < TPM_HEADER_SIZE + 4 * nr_handles)
-			goto err_len;
+	i = tpm2_find_cc(chip, cc);
+	if (i < 0) {
+		dev_dbg(&chip->dev, "0x%04X is an invalid command\n",
+			cc);
+		return -EOPNOTSUPP;
 	}
 
+	attrs = chip->cc_attrs_tbl[i];
+	nr_handles =
+		4 * ((attrs >> TPM2_CC_ATTR_CHANDLES) & GENMASK(2, 0));
+	if (len < TPM_HEADER_SIZE + 4 * nr_handles)
+		goto err_len;
+
 	return cc;
 err_len:
 	dev_dbg(&chip->dev, "%s: insufficient command length %zu", __func__,
@@ -308,7 +307,7 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
 	if (!space)
 		return 0;
 
-	cc = tpm_validate_command(chip, space, cmd, cmdsiz);
+	cc = tpm_find_and_validate_cc(chip, space, cmd, cmdsiz);
 	if (cc < 0)
 		return cc;
 
-- 
2.19.1


--UlVJffcvxoiEqYs2--