syzbot

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BUG: KCSAN: data-race in get_task_mm / stop_this_handle

write to 0xffff8880123a502c of 4 bytes by task 19787 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_rename2+0x10ed/0x32c0 fs/ext4/namei.c:4084
 vfs_rename+0x903/0xe60 fs/namei.c:4312
 do_renameat2+0x5c3/0x900 fs/namei.c:4457
 __do_sys_rename fs/namei.c:4508 [inline]
 __se_sys_rename fs/namei.c:4506 [inline]
 __x64_sys_rename+0x58/0x60 fs/namei.c:4506
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880123a502c of 4 bytes by task 4880 on cpu 0:
 get_task_mm+0x3e/0x90 kernel/fork.c:1212
 get_task_cmdline fs/proc/base.c:348 [inline]
 proc_pid_cmdline_read+0x87/0x650 fs/proc/base.c:368
 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+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4880 Comm: systemd-journal Not tainted 5.11.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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