syzbot

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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getattr

read-write to 0xffff8881047c33b0 of 8 bytes by task 8192 on cpu 1:
 shmem_add_to_page_cache+0x3bb/0x4b0 mm/shmem.c:901
 shmem_alloc_and_add_folio mm/shmem.c:1928 [inline]
 shmem_get_folio_gfp+0x4dd/0xd30 mm/shmem.c:2545
 shmem_get_folio mm/shmem.c:2651 [inline]
 shmem_write_begin+0xa7/0x190 mm/shmem.c:3301
 generic_perform_write+0x189/0x4b0 mm/filemap.c:4102
 shmem_file_write_iter+0xc2/0xe0 mm/shmem.c:3477
 __kernel_write_iter+0x243/0x4c0 fs/read_write.c:617
 dump_emit_page fs/coredump.c:885 [inline]
 dump_user_range+0x5ed/0x8b0 fs/coredump.c:959
 elf_core_dump+0x1d61/0x1ef0 fs/binfmt_elf.c:2128
 do_coredump+0x1814/0x1f50 fs/coredump.c:759
 get_signal+0xd56/0x1000 kernel/signal.c:3020
 arch_do_signal_or_restart+0x9a/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 0xffff8881047c33b0 of 8 bytes by task 20278 on cpu 0:
 shmem_getattr+0x69/0x200 mm/shmem.c:1237
 vfs_getattr_nosec fs/stat.c:208 [inline]
 vfs_getattr+0x172/0x1b0 fs/stat.c:246
 vfs_statx_path fs/stat.c:283 [inline]
 vfs_statx+0x12c/0x310 fs/stat.c:349
 vfs_fstatat+0xe4/0x130 fs/stat.c:368
 __do_sys_newfstatat fs/stat.c:532 [inline]
 __se_sys_newfstatat+0x58/0x260 fs/stat.c:526
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:526
 x64_sys_call+0x2d6f/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000004fb -> 0x00000000000004fd

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 20278 Comm: syz-executor Not tainted 6.14.0-syzkaller-01103-g2df0c02dab82 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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