Re: KASAN: slab-out-of-bounds Read in hidraw_ioctl

From: Alan Stern
Date: Wed Aug 21 2019 - 11:53:54 EST


On Wed, 21 Aug 2019, syzbot wrote:

> Hello,
>
> syzbot has tested the proposed patch but the reproducer still triggered
> crash:
> KASAN: slab-out-of-bounds Read in hidraw_ioctl
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in strlen+0x79/0x90 lib/string.c:525
> Read of size 1 at addr ffff8881d619df38 by task syz-executor.5/2984
>
> CPU: 0 PID: 2984 Comm: syz-executor.5 Not tainted 5.3.0-rc2+ #1
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0xca/0x13e lib/dump_stack.c:113
> print_address_description+0x6a/0x32c mm/kasan/report.c:351
> __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482
> kasan_report+0xe/0x12 mm/kasan/common.c:612
> strlen+0x79/0x90 lib/string.c:525
> strlen include/linux/string.h:281 [inline]
> hidraw_ioctl+0x245/0xae0 drivers/hid/hidraw.c:446
> vfs_ioctl fs/ioctl.c:46 [inline]
> file_ioctl fs/ioctl.c:509 [inline]
> do_vfs_ioctl+0xd2d/0x1330 fs/ioctl.c:696
> ksys_ioctl+0x9b/0xc0 fs/ioctl.c:713
> __do_sys_ioctl fs/ioctl.c:720 [inline]
> __se_sys_ioctl fs/ioctl.c:718 [inline]
> __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:718
> do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x459829
> Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f19881acc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
> RDX: 0000000000000000 RSI: 0000000080404805 RDI: 0000000000000004
> RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f19881ad6d4
> R13: 00000000004c21de R14: 00000000004d5620 R15: 00000000ffffffff

Looks like a test is missing in hidraw_ioctl.

Alan Stern

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

Index: usb-devel/drivers/hid/hidraw.c
===================================================================
--- usb-devel.orig/drivers/hid/hidraw.c
+++ usb-devel/drivers/hid/hidraw.c
@@ -370,7 +370,7 @@ static long hidraw_ioctl(struct file *fi

mutex_lock(&minors_lock);
dev = hidraw_table[minor];
- if (!dev) {
+ if (!dev || !dev->exist) {
ret = -ENODEV;
goto out;
}