[PATCH] driver: input: fix UBSAN warning in input_defuzz_abs_event

liujian
2018-11-02T03:46:00Z

syzkaller triggered a UBCAN warning:

[ 196.188950] UBSAN: Undefined behaviour in drivers/input/input.c:62:23
[ 196.188958] signed integer overflow:
[ 196.188964] -2147483647 - 104 cannot be represented in type 'int [2]'
[ 196.188973] CPU: 7 PID: 4763 Comm: syz-executor Not tainted
4.19.0-514.55.6.9.x86_64+ #7
[ 196.188977] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 196.188979] Call Trace:
[ 196.189001] dump_stack+0x91/0xeb
[ 196.189014] ubsan_epilogue+0x9/0x7c
[ 196.189020] handle_overflow+0x1d7/0x22c
[ 196.189028] ? __ubsan_handle_negate_overflow+0x18f/0x18f
[ 196.189038] ? __mutex_lock+0x213/0x13f0
[ 196.189053] ? drop_futex_key_refs+0xa0/0xa0
[ 196.189070] ? __might_fault+0xef/0x1b0
[ 196.189096] input_handle_event+0xe1b/0x1290
[ 196.189108] input_inject_event+0x1d7/0x27e
[ 196.189119] evdev_write+0x2cf/0x3f0
[ 196.189129] ? evdev_pass_values+0xd40/0xd40
[ 196.189157] ? mark_held_locks+0x160/0x160
[ 196.189171] ? __vfs_write+0xe0/0x6c0
[ 196.189175] ? evdev_pass_values+0xd40/0xd40
[ 196.189179] __vfs_write+0xe0/0x6c0
[ 196.189186] ? kernel_read+0x130/0x130
[ 196.189204] ? _cond_resched+0x15/0x30
[ 196.189214] ? __inode_security_revalidate+0xb8/0xe0
[ 196.189222] ? selinux_file_permission+0x354/0x430
[ 196.189233] vfs_write+0x160/0x440
[ 196.189242] ksys_write+0xc1/0x190
[ 196.189248] ? __ia32_sys_read+0xb0/0xb0
[ 196.189259] ? trace_hardirqs_on_thunk+0x1a/0x1c
[ 196.189267] ? do_syscall_64+0x22/0x4a0
[ 196.189276] do_syscall_64+0xa5/0x4a0
[ 196.189287] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 196.189293] RIP: 0033:0x44e7c9
[ 196.189299] Code: fc ff 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00

the syzkaller reproduce script(but can't reproduce it every time):

r0 = syz_open_dev$evdev(&(0x7f0000000100)='/dev/input/event#\x00', 0x2,
0x1)
write$binfmt_elf64(r0, &(0x7f0000000240)={{0x7f, 0x45, 0x4c, 0x46, 0x40,
0x2, 0x2, 0xffffffff, 0xffffffffffff374c, 0x3, 0x0, 0x80000001, 0x103,
0x40, 0x22e, 0x26, 0x1, 0x38, 0x2, 0xa23, 0x1, 0x2}, [{0x6474e557, 0x5,
0x6, 0x2, 0x9, 0x9, 0x6c3, 0x1ff}], "", [[], [], [], []]}, 0x478)
ioctl$EVIOCGSW(0xffffffffffffffff, 0x8040451b, &(0x7f0000000040)=""/7)
syz_open_dev$evdev(&(0x7f0000000100)='/dev/input/event#\x00', 0x2, 0x1)
r1 = syz_open_dev$evdev(&(0x7f0000000100)='/dev/input/event#\x00', 0x2,
0x1)
openat$smack_task_current(0xffffffffffffff9c,
&(0x7f0000000040)='/proc/self/attr/current\x00', 0x2, 0x0)
ioctl$EVIOCSABS0(r1, 0x401845c0, &(0x7f0000000000)={0x4, 0x10000, 0x4,
0xd1, 0x81, 0x3})
eventfd(0x1ff)
syz_open_dev$evdev(&(0x7f0000000100)='/dev/input/event#\x00', 0x2,
0x200)
syz_open_dev$evdev(&(0x7f0000000100)='/dev/input/event#\x00', 0x2, 0x1)
syz_open_dev$evdev(&(0x7f0000000100)='/dev/input/event#\x00', 0x2, 0x1)
syz_open_dev$evdev(&(0x7f0000000100)='/dev/input/event#\x00', 0x2, 0x1)
syz_open_dev$evdev(&(0x7f0000000100)='/dev/input/event#\x00', 0x2, 0x1)

Typecast int to long to fix the issue.

Signed-off-by: liujian <liujian56@huawei.com>
---
drivers/input/input.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 3304aaa..24615ef 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -59,14 +59,17 @@ static inline int is_event_supported(unsigned int code,
static int input_defuzz_abs_event(int value, int old_val, int fuzz)
{
if (fuzz) {
- if (value > old_val - fuzz / 2 && value < old_val + fuzz / 2)
+ if (value > (long)old_val - fuzz / 2 &&
+ value < (long)old_val + fuzz / 2)
return old_val;

- if (value > old_val - fuzz && value < old_val + fuzz)
- return (old_val * 3 + value) / 4;
+ if (value > (long)old_val - fuzz &&
+ value < (long)old_val + fuzz)
+ return ((long)old_val * 3 + value) / 4;

- if (value > old_val - fuzz * 2 && value < old_val + fuzz * 2)
- return (old_val + value) / 2;
+ if (value > (long)old_val - fuzz * 2 &&
+ value < (long)old_val + fuzz * 2)
+ return ((long)old_val + value) / 2;
}

return value;
--
2.7.4