syzbot

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BUG: KCSAN: data-race in shmem_getattr / shmem_recalc_inode

read-write to 0xffff88811b77ddf8 of 8 bytes by task 32338 on cpu 0:
 shmem_recalc_inode+0x3a/0x1f0 mm/shmem.c:444
 shmem_alloc_and_add_folio mm/shmem.c:2007 [inline]
 shmem_get_folio_gfp+0x7c4/0xd90 mm/shmem.c:2502
 shmem_get_folio mm/shmem.c:2608 [inline]
 shmem_write_begin+0xfc/0x1f0 mm/shmem.c:3239
 generic_perform_write+0x186/0x490 mm/filemap.c:4363
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3414
 __kernel_write_iter+0x30f/0x590 fs/read_write.c:621
 dump_emit_page fs/coredump.c:1298 [inline]
 dump_user_range+0xa73/0xd00 fs/coredump.c:1372
 elf_core_dump+0x21c0/0x2340 fs/binfmt_elf.c:2109
 coredump_write+0xaf9/0xdd0 fs/coredump.c:1052
 do_coredump fs/coredump.c:1131 [inline]
 vfs_coredump+0x2770/0x3290 fs/coredump.c:1200
 get_signal+0xd33/0xf10 kernel/signal.c:3023
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:101 [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:244 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
 irqentry_exit+0x14d/0x610 kernel/entry/common.c:165
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595

read to 0xffff88811b77ddf8 of 8 bytes by task 24643 on cpu 1:
 shmem_getattr+0x41/0x200 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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000001b5b -> 0x0000000000001b5c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 24643 Comm: syz-executor Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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