> -----Original Message----- > From: Jarkko Sakkinen [mailto:jarkko.sakkinen@xxxxxxxxxxxxxxx] > Sent: Wednesday, December 6, 2017 5:32 PM > To: Javier Martinez Canillas <javierm@xxxxxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx; Peter Huewe <peterhuewe@xxxxxx>; Jerry > Snitselaar <jsnitsel@xxxxxxxxxx>; Jason Gunthorpe <jgg@xxxxxxxx>; Tricca, > Philip B <philip.b.tricca@xxxxxxxxx>; Jason Gunthorpe > <jgunthorpe@xxxxxxxxxxxxxxxxxxxx>; linux-integrity@xxxxxxxxxxxxxxx; Roberts, > William C <william.c.roberts@xxxxxxxxx>; James Bottomley > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> > Subject: Re: [PATCH] tpm: return a TPM_RC_COMMAND_CODE response if a > command isn't implemented > > On Mon, Nov 27, 2017 at 12:30:12AM +0100, 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); > > + 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) > > + > > 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, > > }; > > -- > > 2.14.3 > > > > Please use next time --subject-prefix="PATCH v3". > > Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> LGTM Reviewed-by: William Roberts <william.c.roberts@xxxxxxxxx> > > /Jarkko
