syzbot

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BUG: KCSAN: data-race in complete_signal / page_cache_ra_unbounded

write to 0xffff88810252c02c of 4 bytes by task 8361 on cpu 1:
 memalloc_nofs_save include/linux/sched/mm.h:245 [inline]
 page_cache_ra_unbounded+0xae/0x4c0 mm/readahead.c:193
 do_page_cache_ra+0xa7/0xc0 mm/readahead.c:267
 do_sync_mmap_readahead+0x32a/0x360 mm/filemap.c:2810
 filemap_fault+0x1d2/0xc30 mm/filemap.c:2898
 ext4_filemap_fault+0x4b/0x60 fs/ext4/inode.c:6196
 __do_fault mm/memory.c:3637 [inline]
 do_read_fault+0x2e1/0x530 mm/memory.c:3939
 do_fault mm/memory.c:4067 [inline]
 handle_pte_fault mm/memory.c:4318 [inline]
 __handle_mm_fault mm/memory.c:4453 [inline]
 handle_mm_fault+0x1019/0x1840 mm/memory.c:4551
 do_user_addr_fault+0x60c/0xc00 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x94/0x2a0 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577

read to 0xffff88810252c02c of 4 bytes by task 8357 on cpu 0:
 wants_signal kernel/signal.c:982 [inline]
 complete_signal+0x7c/0x600 kernel/signal.c:1005
 __send_signal+0x662/0x780 kernel/signal.c:1185
 send_signal+0x398/0x3e0 kernel/signal.c:1246
 do_send_sig_info+0x9b/0xe0 kernel/signal.c:1295
 do_send_specific+0xc7/0x100 kernel/signal.c:3823
 do_tkill kernel/signal.c:3849 [inline]
 __do_sys_tgkill kernel/signal.c:3868 [inline]
 __se_sys_tgkill kernel/signal.c:3862 [inline]
 __x64_sys_tgkill+0x108/0x140 kernel/signal.c:3862
 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: 8357 Comm: syz-fuzzer Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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