Re: [PATCH] drivers/mt: restrict num_slots in input_mt_init_slots()
From: Sabyrzhan Tasbolatov <hidden>
Date: 2021-02-26 08:43:58
Also in:
linux-input
On Tue, 2 Feb 2021 18:08:07 +0600, Sabyrzhan Tasbolatov wrote:
quoted hunk ↗ jump to hunk
syzbot found WARNING in input_mt_init_slots [1] when struct_size(mt, slots, num_slots)=0x40006 where num_slots=0x10001, which exceeds KMALLOC_MAX_SIZE (0x40000) and causes order >= MAX_ORDER condition. [1] Call Trace: alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267 alloc_pages include/linux/gfp.h:547 [inline] kmalloc_order+0x2e/0xb0 mm/slab_common.c:837 kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853 kmalloc include/linux/slab.h:557 [inline] kzalloc include/linux/slab.h:682 [inline] input_mt_init_slots drivers/input/input-mt.c:49 [inline] Reported-by: syzbot+0122fa359a69694395d5@syzkaller.appspotmail.com Signed-off-by: Sabyrzhan Tasbolatov <redacted> --- drivers/input/input-mt.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c index 44fe6f2f063c..e542f45a45ab 100644 --- a/drivers/input/input-mt.c +++ b/drivers/input/input-mt.c@@ -40,13 +40,18 @@ int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots, { struct input_mt *mt = dev->mt; int i; + size_t mt_size = 0; if (!num_slots) return 0; if (mt) return mt->num_slots != num_slots ? -EINVAL : 0; - mt = kzalloc(struct_size(mt, slots, num_slots), GFP_KERNEL); + mt_size = struct_size(mt, slots, num_slots); + if (mt_size > KMALLOC_MAX_SIZE) + return -ENOMEM; + + mt = kzalloc(mt_size, GFP_KERNEL); if (!mt) goto err_mem;--
Following-up. I've also just found out that in this function, there is another
allocation with num_slots length:
int input_mt_init_slots(..)
{
..
if (flags & INPUT_MT_TRACK) {
unsigned int n2 = num_slots * num_slots;
mt->red = kcalloc(n2, sizeof(*mt->red), GFP_KERNEL);
..
I've checked HID vendors' xrefs for input_mt_init_slots(), most of them
pass >= 5 value to num_slots parameter. So either we should choose some
optimal limit of num_slots or just restrict it with big KMALLOC_MAX_SIZE.
Comments?