syzbot

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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getattr

read-write to 0xffff888107ea5f58 of 8 bytes by task 11667 on cpu 1:
 shmem_add_to_page_cache+0x3b9/0x4b0 mm/shmem.c:825
 shmem_alloc_and_add_folio mm/shmem.c:1839 [inline]
 shmem_get_folio_gfp+0x4f6/0xd90 mm/shmem.c:2335
 shmem_get_folio mm/shmem.c:2441 [inline]
 shmem_write_begin+0xa2/0x180 mm/shmem.c:3094
 generic_perform_write+0x1a8/0x4a0 mm/filemap.c:4056
 shmem_file_write_iter+0xc2/0xe0 mm/shmem.c:3269
 __kernel_write_iter+0x24b/0x4e0 fs/read_write.c:612
 dump_emit_page fs/coredump.c:884 [inline]
 dump_user_range+0x3ac/0x550 fs/coredump.c:945
 elf_core_dump+0x1b66/0x1c60 fs/binfmt_elf.c:2127
 do_coredump+0x1736/0x1ce0 fs/coredump.c:758
 get_signal+0xd4f/0x1000 kernel/signal.c:3001
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 irqentry_exit_to_user_mode+0xa7/0x120 kernel/entry/common.c:231
 irqentry_exit+0x12/0x50 kernel/entry/common.c:334
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

read to 0xffff888107ea5f58 of 8 bytes by task 3710 on cpu 0:
 shmem_getattr+0x69/0x200 mm/shmem.c:1162
 vfs_getattr_nosec fs/stat.c:208 [inline]
 vfs_getattr fs/stat.c:246 [inline]
 vfs_statx_path+0x171/0x2d0 fs/stat.c:283
 vfs_statx+0xe1/0x170 fs/stat.c:347
 vfs_fstatat fs/stat.c:366 [inline]
 __do_sys_newfstatat fs/stat.c:530 [inline]
 __se_sys_newfstatat+0xdc/0x300 fs/stat.c:524
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:524
 x64_sys_call+0x236d/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000001405 -> 0x0000000000001406

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3710 Comm: syz-executor Not tainted 6.12.0-syzkaller-01892-g8f7c8b88bda4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
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