Re: KASAN: slab-out-of-bounds Write in lg4ff_init

[Oliver Neukum <oneukum@suse.com>]

Am Montag, den 05.08.2019, 05:38 -0700 schrieb syzbot:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=144c21dc600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> dashboard link: https://syzkaller.appspot.com/bug?extid=94e2b9e9c7d1dd332345
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=169e8542600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10ec8262600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+94e2b9e9c7d1dd332345@syzkaller.appspotmail.com
> 
> usb 1-1: config 0 interface 0 altsetting 0 has 1 endpoint descriptor,  
> different from the interface descriptor's value: 9
> usb 1-1: New USB device found, idVendor=046d, idProduct=c298, bcdDevice=  
> 0.00
> usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
> usb 1-1: config 0 descriptor??
> logitech 0003:046D:C298.0001: unknown main item tag 0x0
> logitech 0003:046D:C298.0001: unknown main item tag 0x0
> logitech 0003:046D:C298.0001: hidraw0: USB HID v0.00 Device [HID 046d:c298]  
> on usb-dummy_hcd.0-1/input0
> BUG: KASAN: slab-out-of-bounds in set_bit  
> include/asm-generic/bitops-instrumented.h:28 [inline]

#syz test: https://github.com/google/kasan.git e96407b4

From 90b712f3e9b9a45996eb0dfe5f489a4502c9f843 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Mon, 5 Aug 2019 16:14:47 +0200
Subject: [PATCH] hid-lg4ff: sanity check for offsets of FF effects

Malicious devices could provide huge offsets which would lead
to setting bits in random kernel memory. Adding a sanity check.

Reported-by: syzbot+94e2b9e9c7d1dd332345@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/hid/hid-lg4ff.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
index cefba038520c..9e63da793a0d 100644
--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -1327,8 +1327,12 @@ int lg4ff_init(struct hid_device *hid)
 	}
 
 	/* Set supported force feedback capabilities */
+	error = -ENODEV;
 	for (j = 0; lg4ff_devices[i].ff_effects[j] >= 0; j++)
-		set_bit(lg4ff_devices[i].ff_effects[j], dev->ffbit);
+		if (lg4ff_devices[i].ff_effects[j] < FF_CNT)
+			set_bit(lg4ff_devices[i].ff_effects[j], dev->ffbit);
+		else
+			goto err_init;
 
 	error = input_ff_create_memless(dev, NULL, lg4ff_play);
 
-- 
2.16.4