syzbot

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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getattr

read-write to 0xffff88811c07ccf0 of 8 bytes by task 13442 on cpu 1:
 shmem_add_to_page_cache+0x4b2/0x5b0 mm/shmem.c:926
 shmem_alloc_and_add_folio mm/shmem.c:2001 [inline]
 shmem_get_folio_gfp+0x4f3/0xd60 mm/shmem.c:2564
 shmem_get_folio mm/shmem.c:2670 [inline]
 shmem_write_begin+0xfc/0x1f0 mm/shmem.c:3303
 generic_perform_write+0x183/0x490 mm/filemap.c:4325
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3478
 __kernel_write_iter+0x319/0x590 fs/read_write.c:621
 dump_emit_page fs/coredump.c:1304 [inline]
 dump_user_range+0xa73/0xd00 fs/coredump.c:1378
 elf_core_dump+0x21a2/0x2330 fs/binfmt_elf.c:2109
 coredump_write+0xacc/0xdd0 fs/coredump.c:1053
 do_coredump fs/coredump.c:1132 [inline]
 vfs_coredump+0x26dd/0x31e0 fs/coredump.c:1206
 get_signal+0xd5c/0xf20 kernel/signal.c:3022
 arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:98 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:252 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:323 [inline]
 irqentry_exit+0x140/0x5b0 kernel/entry/common.c:162
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

read to 0xffff88811c07ccf0 of 8 bytes by task 3327 on cpu 0:
 shmem_getattr+0x68/0x200 mm/shmem.c:1290
 vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
 vfs_getattr+0x48/0x60 fs/stat.c:262
 vfs_statx_path+0x28/0x140 fs/stat.c:299
 vfs_statx+0xc4/0x170 fs/stat.c:356
 vfs_fstatat+0x118/0x170 fs/stat.c:373
 __do_sys_newfstatat fs/stat.c:538 [inline]
 __se_sys_newfstatat+0x55/0x3e0 fs/stat.c:532
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:532
 x64_sys_call+0x2c64/0x3020 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000029db -> 0x00000000000029dc

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3327 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
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