[PATCH v2] tpm: Initialize name_size_alg for non-NULL name in tpm_buf_append_name()

[Gunnar Kudrjavets <gunnarku@amazon.com>]

tpm_buf_append_name() supports callers passing a pre-computed name
for handles. When name is non-NULL, the code skips the
tpm2_read_public() path but leaves name_size_alg uninitialized
before it is used as the memcpy size argument.

No current in-tree caller passes a non-NULL name, but future use
cases such as name caching would exercise this path. Initialize
name_size_alg by calling name_size() on the caller-provided name,
sharing the error check and assignment with the existing
tpm2_read_public() path. This prevents unmasking a latent bug when
the non-NULL name path is eventually used.

Assisted-by: Kiro:claude-opus-4.6
Reviewed-by: Justinien Bouron <jbouron@amazon.com>
Reviewed-by: Muhammad Hammad Ijaz <mhijaz@amazon.com>
Signed-off-by: Gunnar Kudrjavets <gunnarku@amazon.com>
---
 drivers/char/tpm/tpm2-sessions.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index c4da6fde748f..795cd99dc6fe 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -285,11 +285,14 @@ int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 	    mso == TPM2_MSO_NVRAM) {
 		if (!name) {
 			ret = tpm2_read_public(chip, handle, auth->name[slot]);
-			if (ret < 0)
-				goto err;
-
-			name_size_alg = ret;
+		} else {
+			ret = name_size(name);
 		}
+
+		if (ret < 0)
+			goto err;
+
+		name_size_alg = ret;
 	} else {
 		if (name) {
 			dev_err(&chip->dev, "handle 0x%08x does not use a name\n",

base-commit: 44bd97559c26bb4d7abac09d29e58a4152d88567
--
2.47.3