Prevent invalid (0, 0) inputs to hid-core's snto32() function.
Maybe it is just the dummy device here that is causing this, but
there are hundreds of calls to snto32(0, 0). Having n (bits count)
of 0 is causing the current UBSAN trap with a shift value of
0xffffffff (-1, or n - 1 in this function).
Either of the value to shift being 0 or the bits count being 0 can be
handled by just returning 0 to the caller, avoiding the following
complex shift + OR operations:
return value & (1 << (n - 1)) ? value | (~0U << n) : value;
Fixes: dde5845a529f ("[PATCH] Generic HID layer - code split")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Reported-by: syzbot+1e911ad71dd4ea72e04a@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Jiri Kosina <jikos@xxxxxxxxxx>
Cc: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
Cc: linux-input@xxxxxxxxxxxxxxx
---
drivers/hid/hid-core.c | 3 +++
1 file changed, 3 insertions(+)
--- lnx-510.orig/drivers/hid/hid-core.c
+++ lnx-510/drivers/hid/hid-core.c
@@ -1307,6 +1307,9 @@ EXPORT_SYMBOL_GPL(hid_open_report);
static s32 snto32(__u32 value, unsigned n)
{
+ if (!value || !n)
+ return 0;
+
switch (n) {
case 8: return ((__s8)value);
case 16: return ((__s16)value);
