| Message ID | 20201217011221.25678-1-rdunlap@infradead.org |
|---|---|
| State | Accepted |
| Commit | a0312af1f94d13800e63a7d0a66e563582e39aec |
| Headers | show |
| Series | HID: core: detect and skip invalid inputs to snto32() | expand |
On Wed, 16 Dec 2020, Randy Dunlap wrote: > 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@infradead.org> > Reported-by: syzbot+1e911ad71dd4ea72e04a@syzkaller.appspotmail.com > Cc: Jiri Kosina <jikos@kernel.org> > Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com> > Cc: linux-input@vger.kernel.org > --- > 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; > + Given the fact that this has been in the code basically since ever, we're probably fine, but it's good to have this fixed nevertheless. Applied conservatively to hid.git#for-5.12/core. Thanks, -- Jiri Kosina SUSE Labs
--- 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);
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@infradead.org> Reported-by: syzbot+1e911ad71dd4ea72e04a@syzkaller.appspotmail.com Cc: Jiri Kosina <jikos@kernel.org> Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com> Cc: linux-input@vger.kernel.org --- drivers/hid/hid-core.c | 3 +++ 1 file changed, 3 insertions(+)