On Mon, Feb 04, 2019 at 10:09:51PM +0000, Winkler, Tomas wrote: > > > > The current approach to read first 6 bytes from the response and then tail > > of > > the response, can cause the 2nd memcpy_fromio() to do an unaligned read > > (e.g. read 32-bit word from address aligned to a 16-bits), depending on how > > memcpy_fromio() is implemented. If this happens, the read will fail and the > > memory controller will fill the read with 1's. > > > > This was triggered by 170d13ca3a2f, which should be probably refined to > > check > > and react to the address alignment. Before that commit, on x86 > > memcpy_fromio() turned out to be memcpy(). By a luck GCC has done the right > > thing (from tpm_crb's perspective) for us so far, but we should not rely on > > that. > > Thus, it makes sense to fix this also in tpm_crb, not least because the fix > > can be > > then backported to stable kernels and make them more robust when compiled > > in differing environments. > > > > Cc: sta...@vger.kernel.org > > Cc: James Morris <jmor...@namei.org> > > Cc: Tomas Winkler <tomas.wink...@intel.com> > > Cc: Jerry Snitselaar <jsnit...@redhat.com> > > Fixes: 30fc8d138e91 ("tpm: TPM 2.0 CRB Interface") > > Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com> > > Reviewed-by: Jerry Snitselaar <jsnit...@redhat.com> > After fixing the typos you can add my ack. > Thanks > Tomas > > > --- > > v2: > > * There was a trailing double colon in the end of the short summary. > > * Check requested and expected length against TPM_HEADER_SIZE. > > * Add some explanatory comments to crb_recv(). > > drivers/char/tpm/tpm_crb.c | 22 ++++++++++++++++------ > > 1 file changed, 16 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c index > > 36952ef98f90..c084e61299aa 100644 > > --- a/drivers/char/tpm/tpm_crb.c > > +++ b/drivers/char/tpm/tpm_crb.c > > @@ -287,19 +287,29 @@ static int crb_recv(struct tpm_chip *chip, u8 *buf, > > size_t count) > > struct crb_priv *priv = dev_get_drvdata(&chip->dev); > > unsigned int expected; > > > > - /* sanity check */ > > - if (count < 6) > > + /* A sanity check that the upper layer wants to get at least the header > > + * as that is the minimum size for any TPM response. > > + */ > > + if (count < TPM_HEADER_SIZE) > > return -EIO; > > > > + /* If this bit is set, according to the spec, the TPM is in unrecovable > > ^^^ typo ^^^^ > > + * condition. > > + */ > > if (ioread32(&priv->regs_t->ctrl_sts) & CRB_CTRL_STS_ERROR) > > return -EIO; > > > > - memcpy_fromio(buf, priv->rsp, 6); > > - expected = be32_to_cpup((__be32 *) &buf[2]); > > - if (expected > count || expected < 6) > > + /* Read 8 bytes (not just 6 bytes, which would cover ^^^ tag and^^^ the > > response > > length > > + * field ^^^s^^^) in order to make sure that the reminding memory > > accesses > > ^^^ remaining^^^ > > will > > + * be aligned. > > + */ > > + memcpy_fromio(buf, priv->rsp, 8); > > + > > + expected = be32_to_cpup((__be32 *)&buf[2]); > > + if (expected > count || expected < TPM_HEADER_SIZE) > > return -EIO; > > > > - memcpy_fromio(&buf[6], &priv->rsp[6], expected - 6); > > + memcpy_fromio(&buf[8], &priv->rsp[8], expected - 8); > > > > return expected; > > } > > -- > > 2.19.1 >
Thanks! /Jarkko