On 11/26/2017 03:30 PM, Javier Martinez Canillas wrote: > According to the TPM Library Specification, a TPM device must do a command > header validation before processing and return a TPM_RC_COMMAND_CODE code > if the command is not implemented. > > So user-space will expect to handle that response as an error. But if the > in-kernel resource manager is used (/dev/tpmrm?), an -EINVAL errno code is > returned instead if the command isn't implemented. This confuses userspace > since it doesn't expect that error value. > > This also isn't consistent with the behavior when not using TPM spaces and > accessing the TPM directly (/dev/tpm?). In this case, the command is sent > to the TPM even when not implemented and the TPM responds with an error. > > Instead of returning an -EINVAL errno code when the tpm_validate_command() > function fails, synthesize a TPM command response so user-space can get a > TPM_RC_COMMAND_CODE as expected when a chip doesn't implement the command. > > The TPM only sets 12 of the 32 bits in the TPM_RC response, so the TSS and > TAB specifications define that higher layers in the stack should use some > of the unused 20 bits to specify from which level of the stack the error > is coming from. > > Since the TPM_RC_COMMAND_CODE response code is sent by the kernel resource > manager, set the error level to the TAB/RM layer so user-space is aware of > this. > > Suggested-by: Jason Gunthorpe <jgg@xxxxxxxx> > Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx> > > --- > > Changes since RFCv2: > - Set the error level to the TAB/RM layer so user-space is aware that the error > is not coming from the TPM (suggested by Philip Tricca and Jarkko Sakkinen). > > Changes since RFCv1: > - Don't pass not validated commands to the TPM, instead return a synthesized > response with the correct TPM return code (suggested by Jason Gunthorpe). > > And example of user-space getting confused by the TPM chardev returning -EINVAL > when sending a not supported TPM command can be seen in this tpm2-tools issue: > > https://github.com/intel/tpm2-tools/issues/621 > > Best regards, > Javier > > drivers/char/tpm/tpm-interface.c | 28 ++++++++++++++++++++-------- > drivers/char/tpm/tpm.h | 8 ++++++++ > 2 files changed, 28 insertions(+), 8 deletions(-) > > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c > index ebe0a1d36d8c..9391811c5f83 100644 > --- a/drivers/char/tpm/tpm-interface.c > +++ b/drivers/char/tpm/tpm-interface.c > @@ -328,7 +328,7 @@ unsigned long tpm_calc_ordinal_duration(struct tpm_chip *chip, > } > EXPORT_SYMBOL_GPL(tpm_calc_ordinal_duration); > > -static bool tpm_validate_command(struct tpm_chip *chip, > +static int tpm_validate_command(struct tpm_chip *chip, > struct tpm_space *space, > const u8 *cmd, > size_t len) > @@ -340,10 +340,10 @@ static bool tpm_validate_command(struct tpm_chip *chip, > unsigned int nr_handles; > > if (len < TPM_HEADER_SIZE) > - return false; > + return -EINVAL; > > if (!space) > - return true; > + return 0; > > if (chip->flags & TPM_CHIP_FLAG_TPM2 && chip->nr_commands) { > cc = be32_to_cpu(header->ordinal); > @@ -352,7 +352,7 @@ static bool tpm_validate_command(struct tpm_chip *chip, > if (i < 0) { > dev_dbg(&chip->dev, "0x%04X is an invalid command\n", > cc); > - return false; > + return -EOPNOTSUPP; > } > > attrs = chip->cc_attrs_tbl[i]; > @@ -362,11 +362,11 @@ static bool tpm_validate_command(struct tpm_chip *chip, > goto err_len; > } > > - return true; > + return 0; > err_len: > dev_dbg(&chip->dev, > "%s: insufficient command length %zu", __func__, len); > - return false; > + return -EINVAL; > } > > /** > @@ -391,8 +391,20 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space, > unsigned long stop; > bool need_locality; > > - if (!tpm_validate_command(chip, space, buf, bufsiz)) > - return -EINVAL; > + rc = tpm_validate_command(chip, space, buf, bufsiz); > + if (rc == -EINVAL) > + return rc; > + /* > + * If the command is not implemented by the TPM, synthesize a > + * response with a TPM2_RC_COMMAND_CODE return for user-space. > + */ > + if (rc == -EOPNOTSUPP) { > + header->length = cpu_to_be32(sizeof(*header)); > + header->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS); > + header->return_code = cpu_to_be32(TPM2_RC_COMMAND_CODE | > + TPM2_RESMGRTPM_ERROR_LEVEL); This addresses my previous concern: The 'level' field in the response code will now be set appropriately to TPM2_RESMGRTPM_ERROR_LEVEL. > + return bufsiz; > + } > > if (bufsiz > TPM_BUFSIZE) > bufsiz = TPM_BUFSIZE; > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h > index c1866cc02e30..b3f9108d3d1f 100644 > --- a/drivers/char/tpm/tpm.h > +++ b/drivers/char/tpm/tpm.h > @@ -94,12 +94,20 @@ enum tpm2_structures { > TPM2_ST_SESSIONS = 0x8002, > }; > > +/* Indicates from what level of the software stack the error comes from */ > +#define TPM2_RC_LEVEL_SHIFT 16 > + > +#define TPM2_RESMGRTPM_ERROR_LEVEL (11 << TPM2_RC_LEVEL_SHIFT) > +#define TPM2_RESMGR_ERROR_LEVEL (12 << TPM2_RC_LEVEL_SHIFT) > +#define TPM2_DRIVER_ERROR_LEVEL (13 << TPM2_RC_LEVEL_SHIFT) These last two macros aren't used though they are relevant to the driver / resource mgmt code. Not sure you want to include them until / unless they're needed? This is IMHO cosmetic so feel free to ignore this comment. > + > enum tpm2_return_codes { > TPM2_RC_SUCCESS = 0x0000, > TPM2_RC_HASH = 0x0083, /* RC_FMT1 */ > TPM2_RC_HANDLE = 0x008B, > TPM2_RC_INITIALIZE = 0x0100, /* RC_VER1 */ > TPM2_RC_DISABLED = 0x0120, > + TPM2_RC_COMMAND_CODE = 0x0143, > TPM2_RC_TESTING = 0x090A, /* RC_WARN */ > TPM2_RC_REFERENCE_H0 = 0x0910, > }; > Thanks for incorporating my feedback into your patch. Feel free to add the appropriate tag to the commit message to document my review if it's appropriate. Philip
