==================================================================
BUG: KCSAN: data-race in generic_write_end / next_uptodate_folio

write to 0xffff8881065840e8 of 8 bytes by task 13860 on cpu 1:
 i_size_write include/linux/fs.h:932 [inline]
 generic_write_end+0x94/0x230 fs/buffer.c:2292
 fat_write_end+0x4e/0x160 fs/fat/inode.c:244
 cont_expand_zero fs/buffer.c:2517 [inline]
 cont_write_begin+0x2c0/0x690 fs/buffer.c:2575
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_cont_expand_simple+0xa7/0x140 fs/buffer.c:2476
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_setattr+0x2a9/0x840 fs/fat/file.c:513
 notify_change+0x866/0x8e0 fs/attr.c:499
 do_truncate+0x116/0x150 fs/open.c:66
 do_sys_ftruncate+0x2ba/0x3b0 fs/open.c:194
 __do_sys_ftruncate fs/open.c:205 [inline]
 __se_sys_ftruncate fs/open.c:203 [inline]
 __x64_sys_ftruncate+0x33/0x40 fs/open.c:203
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881065840e8 of 8 bytes by task 13866 on cpu 0:
 i_size_read include/linux/fs.h:910 [inline]
 next_uptodate_folio+0x5bb/0x6e0 mm/filemap.c:3459
 filemap_map_pages+0x5f4/0x730 mm/filemap.c:3607
 do_fault_around mm/memory.c:4525 [inline]
 do_read_fault mm/memory.c:4558 [inline]
 do_fault mm/memory.c:4705 [inline]
 do_pte_missing mm/memory.c:3669 [inline]
 handle_pte_fault mm/memory.c:4978 [inline]
 __handle_mm_fault mm/memory.c:5119 [inline]
 handle_mm_fault+0x1116/0x2cc0 mm/memory.c:5284
 faultin_page mm/gup.c:956 [inline]
 __get_user_pages+0x402/0xe40 mm/gup.c:1239
 populate_vma_page_range mm/gup.c:1666 [inline]
 __mm_populate+0x216/0x330 mm/gup.c:1775
 mm_populate include/linux/mm.h:3305 [inline]
 vm_mmap_pgoff+0x1a7/0x240 mm/util.c:551
 ksys_mmap_pgoff+0x2b8/0x330 mm/mmap.c:1400
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x000000000018b000 -> 0x000000000018c000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13866 Comm: syz-executor.1 Not tainted 6.6.0-rc6-syzkaller-00029-g213f891525c2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
==================================================================