syzbot

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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getattr

read-write to 0xffff88810472d0d0 of 8 bytes by task 32431 on cpu 1:
 shmem_add_to_page_cache+0x37f/0x490 mm/shmem.c:914
 shmem_alloc_and_add_folio mm/shmem.c:1919 [inline]
 shmem_get_folio_gfp+0x4e8/0xd40 mm/shmem.c:2533
 shmem_get_folio mm/shmem.c:2639 [inline]
 shmem_write_begin+0xa8/0x190 mm/shmem.c:3289
 generic_perform_write+0x181/0x490 mm/filemap.c:4103
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3464
 __kernel_write_iter+0x253/0x4c0 fs/read_write.c:617
 dump_emit_page fs/coredump.c:885 [inline]
 dump_user_range+0x5f4/0x8d0 fs/coredump.c:959
 elf_core_dump+0x1dc2/0x1f80 fs/binfmt_elf.c:2128
 do_coredump+0x1836/0x1f40 fs/coredump.c:759
 get_signal+0xd85/0xf70 kernel/signal.c:3019
 arch_do_signal_or_restart+0x97/0x480 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+0x5e/0xa0 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 0xffff88810472d0d0 of 8 bytes by task 26768 on cpu 0:
 shmem_getattr+0x68/0x200 mm/shmem.c:1250
 vfs_getattr_nosec+0x143/0x1e0 fs/stat.c:210
 vfs_getattr fs/stat.c:259 [inline]
 vfs_statx_path fs/stat.c:296 [inline]
 vfs_statx+0x11a/0x380 fs/stat.c:353
 vfs_fstatat+0xe1/0x160 fs/stat.c:372
 __do_sys_newfstatat fs/stat.c:536 [inline]
 __se_sys_newfstatat+0x55/0x260 fs/stat.c:530
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:530
 x64_sys_call+0x2c22/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000001c8f -> 0x0000000000001c91

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 26768 Comm: syz-executor Not tainted 6.15.0-rc5-syzkaller-00300-g3ce9925823c7 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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