On Sun, Jan 29, 2017 at 10:48:39PM +0530, Nayna wrote: > > > On 01/29/2017 08:10 PM, Jarkko Sakkinen wrote: > > On Fri, Jan 27, 2017 at 10:25:49AM -0500, Nayna Jain wrote: > > > This patch add validation in tpm2_get_pcr_allocation to avoid > > > access beyond response buffer length. > > > > > > Suggested-by: Stefan Berger <stef...@linux.vnet.ibm.com> > > > Signed-off-by: Nayna Jain <na...@linux.vnet.ibm.com> > > > > This validation looks broken to me. > > > > > --- > > > drivers/char/tpm/tpm2-cmd.c | 28 +++++++++++++++++++++++----- > > > 1 file changed, 23 insertions(+), 5 deletions(-) > > > > > > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c > > > index 4aad84c..02c1ea7 100644 > > > --- a/drivers/char/tpm/tpm2-cmd.c > > > +++ b/drivers/char/tpm/tpm2-cmd.c > > > @@ -1008,9 +1008,13 @@ static ssize_t tpm2_get_pcr_allocation(struct > > > tpm_chip *chip) > > > struct tpm2_pcr_selection pcr_selection; > > > struct tpm_buf buf; > > > void *marker; > > > - unsigned int count = 0; > > > + void *end; > > > + void *pcr_select_offset; > > > + unsigned int count; > > > + u32 sizeof_pcr_selection; > > > + u32 resp_len; > > > > Very cosmetic but we almos almost universally use the acronym 'rsp' in > > the TPM driver. > > Sure will update. > > > > > > int rc; > > > - int i; > > > + int i = 0; > > > > Why do you need to initialize it? > > Because in out: count is replaced with i. > And it is replaced because now for loop can break even before reaching > count, because of new buffer checks. > > > > > > > > rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, > > > TPM2_CC_GET_CAPABILITY); > > > if (rc) > > > @@ -1034,15 +1038,29 @@ static ssize_t tpm2_get_pcr_allocation(struct > > > tpm_chip *chip) > > > } > > > > > > marker = &buf.data[TPM_HEADER_SIZE + 9]; > > > + > > > + resp_len = be32_to_cpup((__be32 *)&buf.data[2]); > > > + end = &buf.data[resp_len]; > > > > What if the response contains larger length than the buffer size? > > Isn't this check need to be done in tpm_transmit_cmd for all responses ? > Though, it seems it is not done there as well. > > And to understand what do we expect max buffer length. PAGE_SIZE or > TPM_BUFSIZE ?
Oops. You are correct it is done there: if (len != be32_to_cpu(header->length)) return -EFAULT; So need to do this. /Jarkko /Jarkko ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ tpmdd-devel mailing list tpmdd-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tpmdd-devel