Re: KASAN: stack-out-of-bounds Read in update_cfs_group

[Dmitry Vyukov]

On Wed, Jul 4, 2018 at 5:11 PM, syzbot
<syzbot+3d9a14b389b1d7e54d6d@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    2bdea157b999 Merge branch 'sctp-fully-support-for-dscp-and..
> git tree:       bpf-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=153954c2400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f62553dc846b0692
> dashboard link: https://syzkaller.appspot.com/bug?extid=3d9a14b389b1d7e54d6d
> 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+3d9a14b389b1d7e54d6d@xxxxxxxxxxxxxxxxxxxxxxxxx

#syz dup: KASAN: stack-out-of-bounds Read in timerqueue_add

> ==================================================================
> PANIC: double fault, error_code: 0x0
> BUG: KASAN: stack-out-of-bounds in __read_once_size
> include/linux/compiler.h:188 [inline]
> BUG: KASAN: stack-out-of-bounds in calc_group_shares
> kernel/sched/fair.c:2931 [inline]
> BUG: KASAN: stack-out-of-bounds in update_cfs_group+0x4b1/0x590
> kernel/sched/fair.c:3028
> CPU: 1 PID: 15263 Comm: syz-executor7 Not tainted 4.18.0-rc3+ #45
> Read of size 8 at addr ffff8801aca4b500 by task syz-executor5/15250
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:__lock_acquire+0x2e/0x5020 kernel/locking/lockdep.c:3294
>
> Code: 41
> CPU: 0 PID: 15250 Comm: syz-executor5 Not tainted 4.18.0-rc3+ #45
> 57 41
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> 89 cf
> Call Trace:
> 41 56
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
> 41 55
> 49 89
> fd 41
> 54 45
> 89
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
> cc 53
> 65 4c
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
> 8b 34
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
> 25 40
>  __read_once_size include/linux/compiler.h:188 [inline]
>  calc_group_shares kernel/sched/fair.c:2931 [inline]
>  update_cfs_group+0x4b1/0x590 kernel/sched/fair.c:3028
> ee 01
> 00 48
> 83 e4
> f0 48
>  dequeue_entity+0x400/0x15e0 kernel/sched/fair.c:4322
> 81
> ec 60
> 03 00
> 00 48
> 8b 45
> 10 <89>
> 94 24
> 80
>  dequeue_task_fair+0xf2/0x9e0 kernel/sched/fair.c:5455
> 00 00
> 00 48
> ba 00
> 00 00
> 00 00
> fc ff
> df 48
>  dequeue_task kernel/sched/core.c:762 [inline]
>  deactivate_task+0xf3/0x330 kernel/sched/core.c:778
> 89
>  __schedule+0x9c9/0x1ed0 kernel/sched/core.c:3454
> 84 24
> 98
> RSP: 0018:ffff8801ac5ffe80 EFLAGS: 00010082
> RAX: 0000000000000000 RBX: 1ffff100358c004c RCX: 0000000000000002
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff88f92620
> RBP: ffff8801ac600208 R08: 0000000000000000 R09: 0000000000000000
> R10: ffff8801acc771b8 R11: ffff8801daf236b3 R12: 0000000000000000
> R13: ffffffff88f92620 R14: ffff8801aee52140 R15: 0000000000000002
> FS:  00007fe265cc0700(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffff8801ac5ffe78 CR3: 00000001aaa5e000 CR4: 00000000001406e0
> DR0: 00000000200001c0 DR1: 0000000020000000 DR2: 0000000000000000
>  schedule+0xfb/0x450 kernel/sched/core.c:3548
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
> Call Trace:
>
>
> ---
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