From: Grant Hernandez granthernandez@google.com
commit 2a017fd82c5402b3c8df5e3d6e5165d9e6147dc1 upstream.
The GTCO tablet input driver configures itself from an HID report sent via USB during the initial enumeration process. Some debugging messages are generated during the parsing. A debugging message indentation counter is not bounds checked, leading to the ability for a specially crafted HID report to cause '-' and null bytes be written past the end of the indentation array. As long as the kernel has CONFIG_DYNAMIC_DEBUG enabled, this code will not be optimized out. This was discovered during code review after a previous syzkaller bug was found in this driver.
Signed-off-by: Grant Hernandez granthernandez@google.com Cc: stable@vger.kernel.org Signed-off-by: Dmitry Torokhov dmitry.torokhov@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/input/tablet/gtco.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)
--- a/drivers/input/tablet/gtco.c +++ b/drivers/input/tablet/gtco.c @@ -78,6 +78,7 @@ Scott Hill shill@gtcocalcomp.com
/* Max size of a single report */ #define REPORT_MAX_SIZE 10 +#define MAX_COLLECTION_LEVELS 10
/* Bitmask whether pen is in range */ @@ -223,8 +224,7 @@ static void parse_hid_report_descriptor( char maintype = 'x'; char globtype[12]; int indent = 0; - char indentstr[10] = ""; - + char indentstr[MAX_COLLECTION_LEVELS + 1] = { 0 };
dev_dbg(ddev, "======>>>>>>PARSE<<<<<<======\n");
@@ -350,6 +350,13 @@ static void parse_hid_report_descriptor( case TAG_MAIN_COL_START: maintype = 'S';
+ if (indent == MAX_COLLECTION_LEVELS) { + dev_err(ddev, "Collection level %d would exceed limit of %d\n", + indent + 1, + MAX_COLLECTION_LEVELS); + break; + } + if (data == 0) { dev_dbg(ddev, "======>>>>>> Physical\n"); strcpy(globtype, "Physical"); @@ -369,8 +376,15 @@ static void parse_hid_report_descriptor( break;
case TAG_MAIN_COL_END: - dev_dbg(ddev, "<<<<<<======\n"); maintype = 'E'; + + if (indent == 0) { + dev_err(ddev, "Collection level already at zero\n"); + break; + } + + dev_dbg(ddev, "<<<<<<======\n"); + indent--; for (x = 0; x < indent; x++) indentstr[x] = '-';