BUG: KCSAN: data-race in shmem_file_read_iter / shmem_setattr

write to 0xffff88812c9847b8 of 8 bytes by task 27843 on cpu 1:
 i_size_write include/linux/fs.h:891 [inline]
 shmem_setattr+0x3b0/0x4e0 mm/shmem.c:1115
 notify_change+0x8c3/0x930 fs/attr.c:483
 do_truncate+0x116/0x150 fs/open.c:66
 do_sys_ftruncate+0x2a8/0x3a0 fs/open.c:194
 __do_sys_ftruncate fs/open.c:205 [inline]
 __se_sys_ftruncate fs/open.c:203 [inline]
 __x64_sys_ftruncate+0x33/0x40 fs/open.c:203
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88812c9847b8 of 8 bytes by task 27833 on cpu 0:
 i_size_read include/linux/fs.h:869 [inline]
 shmem_file_read_iter+0x91/0x570 mm/shmem.c:2622
 call_read_iter include/linux/fs.h:1848 [inline]
 generic_file_splice_read+0xe3/0x290 fs/splice.c:403
 do_splice_to fs/splice.c:886 [inline]
 splice_direct_to_actor+0x25a/0x5f0 fs/splice.c:957
 do_splice_direct+0x104/0x180 fs/splice.c:1066
 do_sendfile+0x3b8/0x950 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1316 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000001030 -> 0x0000000000000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 27833 Comm: syz-executor.2 Not tainted 6.3.0-syzkaller-07919-g6e98b09da931 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
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