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BUG: KCSAN: data-race in shmem_file_read_iter / shmem_write_end

write to 0xffff888121069560 of 8 bytes by task 6346 on cpu 1:
 i_size_write include/linux/fs.h:932 [inline]
 shmem_write_end+0x9a/0x470 mm/shmem.c:2741
 generic_perform_write+0x267/0x410 mm/filemap.c:3941
 shmem_file_write_iter+0xc8/0xe0 mm/shmem.c:2893
 call_write_iter include/linux/fs.h:2085 [inline]
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x760/0x8d0 fs/read_write.c:590
 ksys_write+0xeb/0x1a0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:652
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888121069560 of 8 bytes by task 6349 on cpu 0:
 i_size_read include/linux/fs.h:910 [inline]
 shmem_file_read_iter+0x1ee/0x550 mm/shmem.c:2810
 __kernel_read+0x2db/0x510 fs/read_write.c:434
 kernel_read+0xae/0x170 fs/read_write.c:452
 kernel_read_file+0x35b/0x4e0 fs/kernel_read_file.c:93
 init_module_from_file kernel/module/main.c:3132 [inline]
 idempotent_init_module kernel/module/main.c:3169 [inline]
 __do_sys_finit_module kernel/module/main.c:3189 [inline]
 __se_sys_finit_module+0x2d1/0x4f0 kernel/module/main.c:3172
 __x64_sys_finit_module+0x43/0x50 kernel/module/main.c:3172
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000617000 -> 0x000000000061c000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6349 Comm: syz-executor.4 Not tainted 6.7.0-syzkaller-12829-g125514880ddd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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Invalid ELF header magic: != ELF