syzbot

==================================================================
BUG: KCSAN: data-race in proc_cgroup_show / stop_this_handle

write to 0xffff88810250602c of 4 bytes by task 4991 on cpu 1:
 memalloc_nofs_restore include/linux/sched/mm.h:258 [inline]
 stop_this_handle+0x2ae/0x2f0 fs/jbd2/transaction.c:744
 jbd2_journal_stop+0x573/0x6d0 fs/jbd2/transaction.c:1907
 __ext4_journal_stop+0x99/0x110 fs/ext4/ext4_jbd2.c:127
 ext4_dirty_inode+0x9a/0xa0 fs/ext4/inode.c:5945
 __mark_inode_dirty+0x72/0x6f0 fs/fs-writeback.c:2274
 mark_inode_dirty include/linux/fs.h:2189 [inline]
 ext4_setattr+0x36c/0xf60 fs/ext4/inode.c:5512
 notify_change+0x86d/0xa60 fs/attr.c:336
 vfs_utimes+0x2b1/0x3d0 fs/utimes.c:65
 do_utimes_fd fs/utimes.c:118 [inline]
 do_utimes+0xf9/0x1d0 fs/utimes.c:142
 __do_sys_utimensat fs/utimes.c:162 [inline]
 __se_sys_utimensat fs/utimes.c:146 [inline]
 __x64_sys_utimensat+0xac/0x150 fs/utimes.c:146
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810250602c of 4 bytes by task 1 on cpu 0:
 proc_cgroup_show+0x3b3/0x6a0 kernel/cgroup/cgroup.c:5821
 proc_single_show+0x84/0x100 fs/proc/base.c:775
 seq_read_iter+0x2ef/0x910 fs/seq_file.c:227
 seq_read+0x221/0x260 fs/seq_file.c:159
 vfs_read+0x154/0x5d0 fs/read_write.c:494
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1 Comm: systemd Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================