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

[syzbot <syzbot+3d9a14b389b1d7e54d6d@syzkaller.appspotmail.com>]

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@syzkaller.appspotmail.com

==================================================================
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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