| Message ID | 1473596340-11376-1-git-send-email-jarkko.sakkinen@linux.intel.com |
|---|---|
| State | New |
| Headers | show |
On Sun, Sep 11, 2016 at 03:19:00PM +0300, Jarkko Sakkinen wrote: > tpm_write() does not check whether the buffer has at least enough space > for the header before passing it to tpm_transmit() so an overflow can > happen. > > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> This is usable neither as read nor write primitive for an exploit. Still it makes sense to validate the input here. /Jarkko > --- > drivers/char/tpm/tpm-interface.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c > index fd863ff..6a67f7f 100644 > --- a/drivers/char/tpm/tpm-interface.c > +++ b/drivers/char/tpm/tpm-interface.c > @@ -337,6 +337,9 @@ ssize_t tpm_transmit(struct tpm_chip *chip, const u8 *buf, size_t bufsiz, > u32 count, ordinal; > unsigned long stop; > > + if (bufsiz < TPM_HEADER_SIZE) > + return -EINVAL; > + > if (bufsiz > TPM_BUFSIZE) > bufsiz = TPM_BUFSIZE; > > -- > 2.7.4 > ------------------------------------------------------------------------------
On Sun, Sep 11, 2016 at 03:51:42PM +0300, Jarkko Sakkinen wrote: > On Sun, Sep 11, 2016 at 03:19:00PM +0300, Jarkko Sakkinen wrote: > > tpm_write() does not check whether the buffer has at least enough space > > for the header before passing it to tpm_transmit() so an overflow can > > happen. > > > > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> > > This is usable neither as read nor write primitive for an exploit. Still > it makes sense to validate the input here. Cannot add fixes line for this one as it's from pre-GIT times... /Jarkko ------------------------------------------------------------------------------
On Sun, Sep 11, 2016 at 03:19:00PM +0300, Jarkko Sakkinen wrote: > tpm_write() does not check whether the buffer has at least enough space > for the header before passing it to tpm_transmit() so an overflow can > happen. Eh? tpm_write uses a hard wired buffer size of TPM_BUFSIZE when working with tpm_transmit. in_size is never used except for the copy. We should probably fix that to sanity check the header length vs in_size. That doesn't seem to be a security issue however because the header length is propery limited to TPM_BUFSIZE and the data buffer is allocated specifically for that process using kzalloc. Jason ------------------------------------------------------------------------------
On Sun, Sep 11, 2016 at 10:05:46PM -0600, Jason Gunthorpe wrote: > On Sun, Sep 11, 2016 at 03:19:00PM +0300, Jarkko Sakkinen wrote: > > tpm_write() does not check whether the buffer has at least enough space > > for the header before passing it to tpm_transmit() so an overflow can > > happen. > > Eh? > > tpm_write uses a hard wired buffer size of TPM_BUFSIZE when working > with tpm_transmit. > > in_size is never used except for the copy. We should probably fix that > to sanity check the header length vs in_size. > > That doesn't seem to be a security issue however because the header > length is propery limited to TPM_BUFSIZE and the data buffer is > allocated specifically for that process using kzalloc. I was working on something else when I bumped into this. The commit message is not the best possible but still the issue is valid although it does not cause any imaginable harm because there is always TPM_BUFSIZE of room in the buffer passed by tpm_write. I'll update the commit message not to speak about tpm_write. "tpm_transmit() does not check whether the bufsiz can contain the TPM header. Add check for this and return -EINVAL if it the buffer is too small." The check should be in tpm_transmit() and also the commit message should be only about that. > Jason /Jarkko ------------------------------------------------------------------------------
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c index fd863ff..6a67f7f 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -337,6 +337,9 @@ ssize_t tpm_transmit(struct tpm_chip *chip, const u8 *buf, size_t bufsiz, u32 count, ordinal; unsigned long stop; + if (bufsiz < TPM_HEADER_SIZE) + return -EINVAL; + if (bufsiz > TPM_BUFSIZE) bufsiz = TPM_BUFSIZE;
tpm_write() does not check whether the buffer has at least enough space for the header before passing it to tpm_transmit() so an overflow can happen. Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> --- drivers/char/tpm/tpm-interface.c | 3 +++ 1 file changed, 3 insertions(+)