tpm: st33zp24: Validate locality read result

check_locality() treats every nonzero transport return as success. SPI
errors remain negative, while the I2C path can convert a negative write
error through its byte-sized status variable. Either result is nonzero
even though the TPM_ACCESS byte can remain unwritten, so indeterminate
ACTIVE_LOCALITY and VALID bits can falsely report an active locality.

Require recv() to return exactly the requested byte before examining
TPM_ACCESS. Transport errors and short reads now report an inactive
locality, while successful reads retain the existing behavior.

This issue was found by a static analysis checker and confirmed by manual
source review.

Fixes: 251a7b08213a ("TPM: STMicroelectronics ST33 I2C KERNEL 3.x")
Signed-off-by: Ruoyu Wang <ruoyuw560@gmail.com>
Link: https://lore.kernel.org/r/20260813153032.3951878-2-ruoyuw560@gmail.com
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

0 files changed, 0 insertions, 0 deletions