On Tue, Oct 24, 2017 at 01:04:03PM +0200, Andrey Konovalov wrote:
> On Tue, Oct 24, 2017 at 7:28 AM, Dmitry Torokhov
> <dmitry.torok...@gmail.com> wrote:
> > parse_hid_report_descriptor() has a while (i < length) loop, which
> > only guarantees that there's at least 1 byte in the buffer, but the
> > loop body can read multiple bytes which causes out-of-bounds access.
> >
> > Reported-by: Andrey Konovalov <andreyk...@google.com>
> > Signed-off-by: Dmitry Torokhov <dmitry.torok...@gmail.com>
> > ---
> > drivers/input/tablet/gtco.c | 24 +++++++++++++++++-------
> > 1 file changed, 17 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/input/tablet/gtco.c b/drivers/input/tablet/gtco.c
> > index b796e891e2ee..0351203b8c24 100644
> > --- a/drivers/input/tablet/gtco.c
> > +++ b/drivers/input/tablet/gtco.c
> > @@ -230,13 +230,24 @@ static void parse_hid_report_descriptor(struct gtco
> > *device, char * report,
> >
> > /* Walk this report and pull out the info we need */
> > while (i < length) {
> > - prefix = report[i];
> > -
> > - /* Skip over prefix */
> > - i++;
> > + prefix = report[i++];
> >
> > /* Determine data size and save the data in the proper
> > variable */
> > - size = PREF_SIZE(prefix);
> > + if (PREF_SIZE(prefix) < 1) {
>
> AFAIU PREF_SIZE(prefix) == 0 is a perfectly valid item data size.
Fair enough. How about the below instead then?
--
Dmitry
Input: gtco - fix potential out-of-bound access
From: Dmitry Torokhov <dmitry.torok...@gmail.com>
parse_hid_report_descriptor() has a while (i < length) loop, which
only guarantees that there's at least 1 byte in the buffer, but the
loop body can read multiple bytes which causes out-of-bounds access.
Reported-by: Andrey Konovalov <andreyk...@google.com>
Signed-off-by: Dmitry Torokhov <dmitry.torok...@gmail.com>
---
drivers/input/tablet/gtco.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/drivers/input/tablet/gtco.c b/drivers/input/tablet/gtco.c
index b796e891e2ee..7d8e9fb831c4 100644
--- a/drivers/input/tablet/gtco.c
+++ b/drivers/input/tablet/gtco.c
@@ -230,13 +230,17 @@ static void parse_hid_report_descriptor(struct gtco
*device, char * report,
/* Walk this report and pull out the info we need */
while (i < length) {
- prefix = report[i];
-
- /* Skip over prefix */
- i++;
+ prefix = report[i++];
/* Determine data size and save the data in the proper variable
*/
- size = PREF_SIZE(prefix);
+ size = (1U << PREF_SIZE(prefix)) >> 1;
+ if (size && i + size >= length) {
+ dev_err(ddev,
+ "Not enough data (need %d, have %d)\n",
+ i + size, length);
+ break;
+ }
+
switch (size) {
case 1:
data = report[i];
@@ -244,8 +248,7 @@ static void parse_hid_report_descriptor(struct gtco
*device, char * report,
case 2:
data16 = get_unaligned_le16(&report[i]);
break;
- case 3:
- size = 4;
+ case 4:
data32 = get_unaligned_le32(&report[i]);
break;
}
