media: firewire: firedtv-avc: fix a buffer overflow in avc_ca_pmt()

  The bounds checking in avc_ca_pmt() is not strict enough.  It should
be checking "read_pos + 4" because it's reading 5 bytes.  If the
"es_info_length" is non-zero then it reads a 6th byte so there needs to
be an additional check for that.

I also added checks for the "write_pos".  I don't think these are
required because "read_pos" and "write_pos" are tied together so
checking one ought to be enough.  But they make the code easier to
understand for me.

The other problem is that "length" can be invalid.  It comes from
"data_length" in fdtv_ca_pmt().

Cc: stable@vger.kernel.org
Reported-by: Luo Likang <luolikang@nsfocus.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
This hardware isn't super common so there is no embargo.  Resending
through normal lists.

Oh, another thing is the data_length calculation in fdtv_ca_pmt() seems
very suspicous.  Reading more than 4 bytes in the loop will lead to
shift wrapping.

 drivers/media/firewire/firedtv-avc.c | 14 +++++++++++---
 drivers/media/firewire/firedtv-ci.c  |  2 ++
 2 files changed, 13 insertions(+), 3 deletions(-)
  

On Wed, Apr 14, 2021 at 11:57:59AM +0300, Dan Carpenter wrote:
> The bounds checking in avc_ca_pmt() is not strict enough.  It should
> be checking "read_pos + 4" because it's reading 5 bytes.  If the
> "es_info_length" is non-zero then it reads a 6th byte so there needs to
> be an additional check for that.
> 
> I also added checks for the "write_pos".  I don't think these are
> required because "read_pos" and "write_pos" are tied together so
> checking one ought to be enough.  But they make the code easier to
> understand for me.
> 
> The other problem is that "length" can be invalid.  It comes from
> "data_length" in fdtv_ca_pmt().
> 
> Cc: stable@vger.kernel.org
> Reported-by: Luo Likang <luolikang@nsfocus.com>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Thanks for the report and the fix!

As a quick note on alternative mitigations, it seems that
CONFIG_UBSAN_BOUNDS would have caught this at runtime too. (i.e.
c->operand[]'s size is known at build time, so out of bounds
indexing should be detected.)

-Kees

> ---
> This hardware isn't super common so there is no embargo.  Resending
> through normal lists.
> 
> Oh, another thing is the data_length calculation in fdtv_ca_pmt() seems
> very suspicous.  Reading more than 4 bytes in the loop will lead to
> shift wrapping.
> 
>  drivers/media/firewire/firedtv-avc.c | 14 +++++++++++---
>  drivers/media/firewire/firedtv-ci.c  |  2 ++
>  2 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/firewire/firedtv-avc.c b/drivers/media/firewire/firedtv-avc.c
> index 2bf9467b917d..71991f8638e6 100644
> --- a/drivers/media/firewire/firedtv-avc.c
> +++ b/drivers/media/firewire/firedtv-avc.c
> @@ -1165,7 +1165,11 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
>  		read_pos += program_info_length;
>  		write_pos += program_info_length;
>  	}
> -	while (read_pos < length) {
> +	while (read_pos + 4 < length) {
> +		if (write_pos + 4 >= sizeof(c->operand) - 4) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
>  		c->operand[write_pos++] = msg[read_pos++];
>  		c->operand[write_pos++] = msg[read_pos++];
>  		c->operand[write_pos++] = msg[read_pos++];
> @@ -1177,13 +1181,17 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
>  		c->operand[write_pos++] = es_info_length >> 8;
>  		c->operand[write_pos++] = es_info_length & 0xff;
>  		if (es_info_length > 0) {
> +			if (read_pos >= length) {
> +				ret = -EINVAL;
> +				goto out;
> +			}
>  			pmt_cmd_id = msg[read_pos++];
>  			if (pmt_cmd_id != 1 && pmt_cmd_id != 4)
>  				dev_err(fdtv->device, "invalid pmt_cmd_id %d at stream level\n",
>  					pmt_cmd_id);
>  
> -			if (es_info_length > sizeof(c->operand) - 4 -
> -					     write_pos) {
> +			if (es_info_length > sizeof(c->operand) - 4 - write_pos ||
> +			    es_info_length > length - read_pos) {
>  				ret = -EINVAL;
>  				goto out;
>  			}
> diff --git a/drivers/media/firewire/firedtv-ci.c b/drivers/media/firewire/firedtv-ci.c
> index 9363d005e2b6..2d6992ac5dd6 100644
> --- a/drivers/media/firewire/firedtv-ci.c
> +++ b/drivers/media/firewire/firedtv-ci.c
> @@ -134,6 +134,8 @@ static int fdtv_ca_pmt(struct firedtv *fdtv, void *arg)
>  	} else {
>  		data_length = msg->msg[3];
>  	}
> +	if (data_length > sizeof(msg->msg) - 4)
> +		return -EINVAL;
>  
>  	return avc_ca_pmt(fdtv, &msg->msg[data_pos], data_length);
>  }
> -- 
> 2.30.2
>
  

This was marked as superseded in patchwork.  What are we going to apply
instead?

regards,
dan carpenter

On Wed, Apr 14, 2021 at 11:57:59AM +0300, Dan Carpenter wrote:
> The bounds checking in avc_ca_pmt() is not strict enough.  It should
> be checking "read_pos + 4" because it's reading 5 bytes.  If the
> "es_info_length" is non-zero then it reads a 6th byte so there needs to
> be an additional check for that.
> 
> I also added checks for the "write_pos".  I don't think these are
> required because "read_pos" and "write_pos" are tied together so
> checking one ought to be enough.  But they make the code easier to
> understand for me.
> 
> The other problem is that "length" can be invalid.  It comes from
> "data_length" in fdtv_ca_pmt().
> 
> Cc: stable@vger.kernel.org
> Reported-by: Luo Likang <luolikang@nsfocus.com>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> This hardware isn't super common so there is no embargo.  Resending
> through normal lists.
> 
> Oh, another thing is the data_length calculation in fdtv_ca_pmt() seems
> very suspicous.  Reading more than 4 bytes in the loop will lead to
> shift wrapping.
> 
>  drivers/media/firewire/firedtv-avc.c | 14 +++++++++++---
>  drivers/media/firewire/firedtv-ci.c  |  2 ++
>  2 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/firewire/firedtv-avc.c b/drivers/media/firewire/firedtv-avc.c
> index 2bf9467b917d..71991f8638e6 100644
> --- a/drivers/media/firewire/firedtv-avc.c
> +++ b/drivers/media/firewire/firedtv-avc.c
> @@ -1165,7 +1165,11 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
>  		read_pos += program_info_length;
>  		write_pos += program_info_length;
>  	}
> -	while (read_pos < length) {
> +	while (read_pos + 4 < length) {
> +		if (write_pos + 4 >= sizeof(c->operand) - 4) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
>  		c->operand[write_pos++] = msg[read_pos++];
>  		c->operand[write_pos++] = msg[read_pos++];
>  		c->operand[write_pos++] = msg[read_pos++];
> @@ -1177,13 +1181,17 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
>  		c->operand[write_pos++] = es_info_length >> 8;
>  		c->operand[write_pos++] = es_info_length & 0xff;
>  		if (es_info_length > 0) {
> +			if (read_pos >= length) {
> +				ret = -EINVAL;
> +				goto out;
> +			}
>  			pmt_cmd_id = msg[read_pos++];
>  			if (pmt_cmd_id != 1 && pmt_cmd_id != 4)
>  				dev_err(fdtv->device, "invalid pmt_cmd_id %d at stream level\n",
>  					pmt_cmd_id);
>  
> -			if (es_info_length > sizeof(c->operand) - 4 -
> -					     write_pos) {
> +			if (es_info_length > sizeof(c->operand) - 4 - write_pos ||
> +			    es_info_length > length - read_pos) {
>  				ret = -EINVAL;
>  				goto out;
>  			}
> diff --git a/drivers/media/firewire/firedtv-ci.c b/drivers/media/firewire/firedtv-ci.c
> index 9363d005e2b6..2d6992ac5dd6 100644
> --- a/drivers/media/firewire/firedtv-ci.c
> +++ b/drivers/media/firewire/firedtv-ci.c
> @@ -134,6 +134,8 @@ static int fdtv_ca_pmt(struct firedtv *fdtv, void *arg)
>  	} else {
>  		data_length = msg->msg[3];
>  	}
> +	if (data_length > sizeof(msg->msg) - 4)
> +		return -EINVAL;
>  
>  	return avc_ca_pmt(fdtv, &msg->msg[data_pos], data_length);
>  }
> -- 
> 2.30.2
  

On Wed, Apr 14, 2021 at 11:57:59AM +0300, Dan Carpenter wrote:
> The bounds checking in avc_ca_pmt() is not strict enough.  It should
> be checking "read_pos + 4" because it's reading 5 bytes.  If the
> "es_info_length" is non-zero then it reads a 6th byte so there needs to
> be an additional check for that.
> 
> I also added checks for the "write_pos".  I don't think these are
> required because "read_pos" and "write_pos" are tied together so
> checking one ought to be enough.  But they make the code easier to
> understand for me.
> 
> The other problem is that "length" can be invalid.  It comes from
> "data_length" in fdtv_ca_pmt().
> 
> Cc: stable@vger.kernel.org
> Reported-by: Luo Likang <luolikang@nsfocus.com>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> This hardware isn't super common so there is no embargo.  Resending
> through normal lists.
> 
> Oh, another thing is the data_length calculation in fdtv_ca_pmt() seems
> very suspicous.  Reading more than 4 bytes in the loop will lead to
> shift wrapping.
> 
>  drivers/media/firewire/firedtv-avc.c | 14 +++++++++++---
>  drivers/media/firewire/firedtv-ci.c  |  2 ++
>  2 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/firewire/firedtv-avc.c b/drivers/media/firewire/firedtv-avc.c
> index 2bf9467b917d..71991f8638e6 100644
> --- a/drivers/media/firewire/firedtv-avc.c
> +++ b/drivers/media/firewire/firedtv-avc.c
> @@ -1165,7 +1165,11 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
>  		read_pos += program_info_length;
>  		write_pos += program_info_length;
>  	}
> -	while (read_pos < length) {
> +	while (read_pos + 4 < length) {
> +		if (write_pos + 4 >= sizeof(c->operand) - 4) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
>  		c->operand[write_pos++] = msg[read_pos++];
>  		c->operand[write_pos++] = msg[read_pos++];
>  		c->operand[write_pos++] = msg[read_pos++];
> @@ -1177,13 +1181,17 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
>  		c->operand[write_pos++] = es_info_length >> 8;
>  		c->operand[write_pos++] = es_info_length & 0xff;
>  		if (es_info_length > 0) {
> +			if (read_pos >= length) {
> +				ret = -EINVAL;
> +				goto out;
> +			}
>  			pmt_cmd_id = msg[read_pos++];
>  			if (pmt_cmd_id != 1 && pmt_cmd_id != 4)
>  				dev_err(fdtv->device, "invalid pmt_cmd_id %d at stream level\n",
>  					pmt_cmd_id);
>  
> -			if (es_info_length > sizeof(c->operand) - 4 -
> -					     write_pos) {
> +			if (es_info_length > sizeof(c->operand) - 4 - write_pos ||
> +			    es_info_length > length - read_pos) {
>  				ret = -EINVAL;
>  				goto out;
>  			}
> diff --git a/drivers/media/firewire/firedtv-ci.c b/drivers/media/firewire/firedtv-ci.c
> index 9363d005e2b6..2d6992ac5dd6 100644
> --- a/drivers/media/firewire/firedtv-ci.c
> +++ b/drivers/media/firewire/firedtv-ci.c
> @@ -134,6 +134,8 @@ static int fdtv_ca_pmt(struct firedtv *fdtv, void *arg)
>  	} else {
>  		data_length = msg->msg[3];
>  	}
> +	if (data_length > sizeof(msg->msg) - 4)
> +		return -EINVAL;
>  
>  	return avc_ca_pmt(fdtv, &msg->msg[data_pos], data_length);
>  }
> -- 
> 2.30.2
> 

This patch seems to have gotten lost.  Any change of it getting applied?

thanks,

greg k-h
  

Hi,

On Thu, Jul 29, 2021 at 12:32:21PM +0200, Greg KH wrote:
> On Wed, Apr 14, 2021 at 11:57:59AM +0300, Dan Carpenter wrote:
> > The bounds checking in avc_ca_pmt() is not strict enough.  It should
> > be checking "read_pos + 4" because it's reading 5 bytes.  If the
> > "es_info_length" is non-zero then it reads a 6th byte so there needs to
> > be an additional check for that.
> > 
> > I also added checks for the "write_pos".  I don't think these are
> > required because "read_pos" and "write_pos" are tied together so
> > checking one ought to be enough.  But they make the code easier to
> > understand for me.
> > 
> > The other problem is that "length" can be invalid.  It comes from
> > "data_length" in fdtv_ca_pmt().
> > 
> > Cc: stable@vger.kernel.org
> > Reported-by: Luo Likang <luolikang@nsfocus.com>
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> > This hardware isn't super common so there is no embargo.  Resending
> > through normal lists.
> > 
> > Oh, another thing is the data_length calculation in fdtv_ca_pmt() seems
> > very suspicous.  Reading more than 4 bytes in the loop will lead to
> > shift wrapping.
> > 
> >  drivers/media/firewire/firedtv-avc.c | 14 +++++++++++---
> >  drivers/media/firewire/firedtv-ci.c  |  2 ++
> >  2 files changed, 13 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/media/firewire/firedtv-avc.c b/drivers/media/firewire/firedtv-avc.c
> > index 2bf9467b917d..71991f8638e6 100644
> > --- a/drivers/media/firewire/firedtv-avc.c
> > +++ b/drivers/media/firewire/firedtv-avc.c
> > @@ -1165,7 +1165,11 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
> >  		read_pos += program_info_length;
> >  		write_pos += program_info_length;
> >  	}
> > -	while (read_pos < length) {
> > +	while (read_pos + 4 < length) {
> > +		if (write_pos + 4 >= sizeof(c->operand) - 4) {
> > +			ret = -EINVAL;
> > +			goto out;
> > +		}
> >  		c->operand[write_pos++] = msg[read_pos++];
> >  		c->operand[write_pos++] = msg[read_pos++];
> >  		c->operand[write_pos++] = msg[read_pos++];
> > @@ -1177,13 +1181,17 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
> >  		c->operand[write_pos++] = es_info_length >> 8;
> >  		c->operand[write_pos++] = es_info_length & 0xff;
> >  		if (es_info_length > 0) {
> > +			if (read_pos >= length) {
> > +				ret = -EINVAL;
> > +				goto out;
> > +			}
> >  			pmt_cmd_id = msg[read_pos++];
> >  			if (pmt_cmd_id != 1 && pmt_cmd_id != 4)
> >  				dev_err(fdtv->device, "invalid pmt_cmd_id %d at stream level\n",
> >  					pmt_cmd_id);
> >  
> > -			if (es_info_length > sizeof(c->operand) - 4 -
> > -					     write_pos) {
> > +			if (es_info_length > sizeof(c->operand) - 4 - write_pos ||
> > +			    es_info_length > length - read_pos) {
> >  				ret = -EINVAL;
> >  				goto out;
> >  			}
> > diff --git a/drivers/media/firewire/firedtv-ci.c b/drivers/media/firewire/firedtv-ci.c
> > index 9363d005e2b6..2d6992ac5dd6 100644
> > --- a/drivers/media/firewire/firedtv-ci.c
> > +++ b/drivers/media/firewire/firedtv-ci.c
> > @@ -134,6 +134,8 @@ static int fdtv_ca_pmt(struct firedtv *fdtv, void *arg)
> >  	} else {
> >  		data_length = msg->msg[3];
> >  	}
> > +	if (data_length > sizeof(msg->msg) - 4)
> > +		return -EINVAL;
> >  
> >  	return avc_ca_pmt(fdtv, &msg->msg[data_pos], data_length);
> >  }
> > -- 
> > 2.30.2
> > 
> 
> This patch seems to have gotten lost.  Any change of it getting applied?

As far I can see there was then a version 2 of the patch, but that one
got list somewhere. Friendly ping on this thread :)

Regards,
Salvatore