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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Wed, 21 Aug 2019 14:57:23 +0200
Message-ID: <CAAeHK+zeN+bLTix2yaWDo-iu_G4D8T1KELjds=KVTtywiPpc4g@mail.gmail.com>
Subject: Re: KASAN: slab-out-of-bounds Read in hidraw_ioctl
To:     syzbot <syzbot+5a6c4ec678a0c6ee84ba@syzkaller.appspotmail.com>
Cc:     Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        Jiri Kosina <jikos@kernel.org>, linux-input@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
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On Sun, Aug 11, 2019 at 10:46 PM syzbot
<syzbot+5a6c4ec678a0c6ee84ba@syzkaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for 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=150426ba600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> dashboard link: https://syzkaller.appspot.com/bug?extid=5a6c4ec678a0c6ee84ba
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12725c02600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=162163c2600000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+5a6c4ec678a0c6ee84ba@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in strlen+0x79/0x90 lib/string.c:525
> Read of size 1 at addr ffff8881d29bdf38 by task syz-executor201/1726
>
> CPU: 1 PID: 1726 Comm: syz-executor201 Not tainted 5.3.0-rc2+ #25
> 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: 0033:0x445679
> Code: e8 5c ad 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 9b cd fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffc8514f3a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000445679
> RDX: 0000000000000000 RSI: 0000000080404805 RDI: 0000000000000004
> RBP: 00000000006d0018 R08: 000000000000000b R09: 00000000004002e0
> R10: 000000000000000f R11: 0000000000000246 R12: 00000000004028a0
> R13: 0000000000402930 R14: 0000000000000000 R15: 0000000000000000
>
> Allocated by task 0:
> (stack is not available)
>
> Freed by task 0:
> (stack is not available)
>
> The buggy address belongs to the object at ffff8881d29bde60
>   which belongs to the cache shmem_inode_cache of size 1168
> The buggy address is located 216 bytes inside of
>   1168-byte region [ffff8881d29bde60, ffff8881d29be2f0)
> The buggy address belongs to the page:
> page:ffffea00074a6f00 refcount:1 mapcount:0 mapping:ffff8881da115180
> index:0x0 compound_mapcount: 0
> flags: 0x200000000010200(slab|head)
> raw: 0200000000010200 dead000000000100 dead000000000122 ffff8881da115180
> raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8881d29bde00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>   ffff8881d29bde80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ffff8881d29bdf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>                                          ^
>   ffff8881d29bdf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>   ffff8881d29be000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>

Trying Alan's fix from another thread here:

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

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