Message-ID: <CACT4Y+ZkEsoP_dHvFuRq9n0nfDiXS63P3Kx20+FeBWQVi_VR0Q@mail.gmail.com>
Date:   Fri, 4 May 2018 07:36:45 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+873ae613c636f037d5f8@...kaller.appspotmail.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Write in process_preds

On Fri, May 4, 2018 at 7:30 AM, syzbot
<syzbot+873ae613c636f037d5f8@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    03f5781be2c7 bpf, x86_32: add eBPF JIT compiler for ia32
> git tree:       bpf-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13627237800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3d356c2d908b7293
> dashboard link: https://syzkaller.appspot.com/bug?extid=873ae613c636f037d5f8
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+873ae613c636f037d5f8@...kaller.appspotmail.com


This looks similar to the old crash with reproducer:

#syz dup: KASAN: slab-out-of-bounds Write in process_preds

https://syzkaller.appspot.com/bug?id=e84ebd53b11608595ca4fd595d48ae9ddce9cf11

> ==================================================================
> BUG: KASAN: use-after-free in predicate_parse
> kernel/trace/trace_events_filter.c:557 [inline]
> BUG: KASAN: use-after-free in process_preds+0x1958/0x19b0
> kernel/trace/trace_events_filter.c:1505
> Write of size 4 at addr ffff8801ada34ff0 by task syz-executor3/6458
>
> CPU: 0 PID: 6458 Comm: syz-executor3 Not tainted 4.17.0-rc2+ #22
> 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+0x1b9/0x294 lib/dump_stack.c:113
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:437
>  predicate_parse kernel/trace/trace_events_filter.c:557 [inline]
>  process_preds+0x1958/0x19b0 kernel/trace/trace_events_filter.c:1505
>  create_filter+0x155/0x270 kernel/trace/trace_events_filter.c:1713
>  ftrace_profile_set_filter+0x130/0x2e0
> kernel/trace/trace_events_filter.c:2038
>  perf_event_set_filter+0x248/0x1230 kernel/events/core.c:9079
>  _perf_ioctl+0x84c/0x15e0 kernel/events/core.c:5059
>  perf_ioctl+0x59/0x80 kernel/events/core.c:5110
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  file_ioctl fs/ioctl.c:500 [inline]
>  do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
>  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
>  __do_sys_ioctl fs/ioctl.c:708 [inline]
>  __se_sys_ioctl fs/ioctl.c:706 [inline]
>  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x455979
> RSP: 002b:00007fd67f515c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fd67f5166d4 RCX: 0000000000455979
> RDX: 0000000020000040 RSI: 0000000040082406 RDI: 0000000000000013
> RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 00000000000002bf R14: 00000000006f8288 R15: 0000000000000000
>
> The buggy address belongs to the page:
> page:ffffea0006b68d00 count:0 mapcount:0 mapping:0000000000000000 index:0x0
> flags: 0x2fffc0000000000()
> raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
> raw: ffff8801daf2fcd8 ffffea0006a5d9e0 0000000000000000 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801ada34e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>  ffff8801ada34f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>
>> ffff8801ada34f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>
>                                                              ^
>  ffff8801ada35000: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>  ffff8801ada35080: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
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