KASAN: use-after-free Read in __schedule

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 2c2101d1 Merge 5.4.23 into android-5.4
git tree: android-5.4
console output: https://syzkaller.appspot.com/x/log.txt?x=16cb1329e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=ad2796651c9ac912
dashboard link: https://syzkaller.appspot.com/bug?extid=d78a0940e37a384dd5b8
compiler: Android (6032204 based on r370808) clang version 10.0.1 (https://android.googlesource.com/toolchain/llvm-project 6e765c10313d15c02ab29977a82938f66742c3a9)

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+d78a09...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in schedule_debug kernel/sched/core.c:3879 [inline]
BUG: KASAN: use-after-free in __schedule+0xf6/0x1700 kernel/sched/core.c:4012
Read of size 8 at addr ffff8881cbd38000 by task syz-executor.3/15020

CPU: 0 PID: 15020 Comm: syz-executor.3 Tainted: G W 5.4.23-syzkaller-01268-g2c2101d18159 #0
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+0x1b0/0x228 lib/dump_stack.c:118
print_address_description+0x96/0x5d0 mm/kasan/report.c:374
__kasan_report+0x14b/0x1c0 mm/kasan/report.c:506
kasan_report+0x26/0x50 mm/kasan/common.c:634
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
schedule_debug kernel/sched/core.c:3879 [inline]
__schedule+0xf6/0x1700 kernel/sched/core.c:4012
schedule+0x136/0x1d0 kernel/sched/core.c:4147
freezable_schedule include/linux/freezer.h:172 [inline]
futex_wait_queue_me+0x286/0x410 kernel/futex.c:2704
futex_wait+0x2c0/0x880 kernel/futex.c:2810
do_futex+0x2416/0x3f90 kernel/futex.c:3881
__do_sys_futex kernel/futex.c:3942 [inline]
__se_sys_futex+0x31d/0x440 kernel/futex.c:3910
__x64_sys_futex+0xe5/0x100 kernel/futex.c:3910
do_syscall_64+0xc0/0x100 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45c479
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0ee4fadcf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 000000000076bf28 RCX: 000000000045c479
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000076bf28
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000076bf2c
R13: 00007ffda6f0802f R14: 00007f0ee4fae9c0 R15: 000000000076bf2c

The buggy address belongs to the page:
page:ffffea00072f4e00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
raw: 8000000000000000 ffffea0007269048 ffffea0007521fc8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881cbd37f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881cbd37f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881cbd38000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff8881cbd38080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8881cbd38100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.