Re: [PATCH] HID: core: fix shift-out-of-bounds in hid_report_raw_event

[Jiri Kosina]

On Wed, 16 Nov 2022, Peng Zhang wrote:

> From: ZhangPeng <zhangpeng362@xxxxxxxxxx>
> 
> Syzbot reported shift-out-of-bounds in hid_report_raw_event.
> 
> microsoft 0003:045E:07DA.0001: hid_field_extract() called with n (128) >
> 32! (swapper/0)
> ======================================================================
> UBSAN: shift-out-of-bounds in drivers/hid/hid-core.c:1323:20
> shift exponent 127 is too large for 32-bit type 'int'
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted
> 6.1.0-rc4-syzkaller-00159-g4bbf3422df78 #0
> Hardware name: Google Compute Engine/Google Compute Engine, BIOS
> Google 10/26/2022
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
>  ubsan_epilogue lib/ubsan.c:151 [inline]
>  __ubsan_handle_shift_out_of_bounds+0x3a6/0x420 lib/ubsan.c:322
>  snto32 drivers/hid/hid-core.c:1323 [inline]
>  hid_input_fetch_field drivers/hid/hid-core.c:1572 [inline]
>  hid_process_report drivers/hid/hid-core.c:1665 [inline]
>  hid_report_raw_event+0xd56/0x18b0 drivers/hid/hid-core.c:1998
>  hid_input_report+0x408/0x4f0 drivers/hid/hid-core.c:2066
>  hid_irq_in+0x459/0x690 drivers/hid/usbhid/hid-core.c:284
>  __usb_hcd_giveback_urb+0x369/0x530 drivers/usb/core/hcd.c:1671
>  dummy_timer+0x86b/0x3110 drivers/usb/gadget/udc/dummy_hcd.c:1988
>  call_timer_fn+0xf5/0x210 kernel/time/timer.c:1474
>  expire_timers kernel/time/timer.c:1519 [inline]
>  __run_timers+0x76a/0x980 kernel/time/timer.c:1790
>  run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1803
>  __do_softirq+0x277/0x75b kernel/softirq.c:571
>  __irq_exit_rcu+0xec/0x170 kernel/softirq.c:650
>  irq_exit_rcu+0x5/0x20 kernel/softirq.c:662
>  sysvec_apic_timer_interrupt+0x91/0xb0 arch/x86/kernel/apic/apic.c:1107
> ======================================================================
> 
> If the size of the integer (unsigned n) is bigger than 32 in snto32(),
> shift exponent will be too large for 32-bit type 'int', resulting in a
> shift-out-of-bounds bug.
> Fix this by adding a check on the size of the integer (unsigned n) in
> snto32(). To add support for n greater than 32 bits, set n to 32, if n
> is greater than 32.
> 
> Reported-by: syzbot+8b1641d2f14732407e23@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: dde5845a529f ("[PATCH] Generic HID layer - code split")
> Signed-off-by: ZhangPeng <zhangpeng362@xxxxxxxxxx>
> ---
>  drivers/hid/hid-core.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 9c1d31f63f85..bd47628da6be 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -1315,6 +1315,9 @@ static s32 snto32(__u32 value, unsigned n)
>  	if (!value || !n)
>  		return 0;
>  
> +	if (n > 32)
> +		n = 32;
> +
>  	switch (n) {
>  	case 8:  return ((__s8)value);

Applied, thanks for fixing this.

-- 
Jiri Kosina
SUSE Labs