syzbot

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BUG: KCSAN: data-race in expire_timers / try_to_del_timer_sync

write to 0xffff888237d376c8 of 8 bytes by interrupt on cpu 1:
 expire_timers+0x13d/0x250 kernel/time/timer.c:1465
 __run_timers+0x358/0x420 kernel/time/timer.c:1732
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1745
 __do_softirq+0x12c/0x26e kernel/softirq.c:558
 invoke_softirq kernel/softirq.c:432 [inline]
 __irq_exit_rcu+0x9a/0xb0 kernel/softirq.c:636
 sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1100
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
 mark_page_accessed+0xcd/0x550 mm/swap.c:430
 touch_buffer fs/buffer.c:63 [inline]
 __find_get_block+0x6fd/0x900 fs/buffer.c:1312
 sb_find_get_block include/linux/buffer_head.h:340 [inline]
 recently_deleted fs/ext4/ialloc.c:687 [inline]
 find_inode_bit+0x181/0x330 fs/ext4/ialloc.c:729
 __ext4_new_inode+0xc7a/0x2f70 fs/ext4/ialloc.c:1064
 ext4_symlink+0x2c3/0x700 fs/ext4/namei.c:3465
 vfs_symlink+0x23a/0x300 fs/namei.c:4182
 do_symlinkat+0xeb/0x280 fs/namei.c:4212
 __do_sys_symlink fs/namei.c:4233 [inline]
 __se_sys_symlink fs/namei.c:4231 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4231
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237d376c8 of 8 bytes by task 11 on cpu 0:
 try_to_del_timer_sync+0xe3/0x290 kernel/time/timer.c:1233
 del_timer_sync kernel/time/timer.c:1380 [inline]
 schedule_timeout+0x108/0x240 kernel/time/timer.c:1880
 rcu_gp_fqs_loop kernel/rcu/tree.c:1996 [inline]
 rcu_gp_kthread+0xbf7/0xec0 kernel/rcu/tree.c:2169
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

value changed: 0xffffc90000277e60 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11 Comm: rcu_sched Not tainted 5.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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