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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getpage_gfp

read-write to 0xffff8881208f38e0 of 8 bytes by task 19568 on cpu 0:
 shmem_add_to_page_cache+0x802/0x8f0 mm/shmem.c:745
 shmem_getpage_gfp+0x7af/0x1750 mm/shmem.c:1939
 shmem_fault+0xd2/0x350 mm/shmem.c:2116
 __do_fault mm/memory.c:4165 [inline]
 do_read_fault mm/memory.c:4514 [inline]
 do_fault+0x500/0xb20 mm/memory.c:4643
 handle_pte_fault mm/memory.c:4907 [inline]
 __handle_mm_fault mm/memory.c:5046 [inline]
 handle_mm_fault+0x889/0xa90 mm/memory.c:5144
 faultin_page mm/gup.c:955 [inline]
 __get_user_pages+0x34a/0xbf0 mm/gup.c:1176
 populate_vma_page_range mm/gup.c:1520 [inline]
 __mm_populate+0x26e/0x3a0 mm/gup.c:1633
 mm_populate include/linux/mm.h:2710 [inline]
 vm_mmap_pgoff+0x160/0x1f0 mm/util.c:557
 ksys_mmap_pgoff+0xc2/0x320 mm/mmap.c:1633
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881208f38e0 of 8 bytes by task 19562 on cpu 1:
 shmem_recalc_inode mm/shmem.c:362 [inline]
 shmem_getpage_gfp+0xd8b/0x1750 mm/shmem.c:1949
 shmem_fault+0xd2/0x350 mm/shmem.c:2116
 __do_fault mm/memory.c:4165 [inline]
 do_shared_fault mm/memory.c:4569 [inline]
 do_fault+0x5df/0xb20 mm/memory.c:4647
 handle_pte_fault mm/memory.c:4907 [inline]
 __handle_mm_fault mm/memory.c:5046 [inline]
 handle_mm_fault+0x889/0xa90 mm/memory.c:5144
 do_user_addr_fault+0x4cd/0x940 arch/x86/mm/fault.c:1397
 handle_page_fault arch/x86/mm/fault.c:1484 [inline]
 exc_page_fault+0x60/0x160 arch/x86/mm/fault.c:1540
 asm_exc_page_fault+0x22/0x30
 copy_user_enhanced_fast_string+0xa/0x40
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:58 [inline]
 copyout lib/iov_iter.c:155 [inline]
 _copy_to_iter+0x19a/0x820 lib/iov_iter.c:667
 copy_to_iter include/linux/uio.h:162 [inline]
 get_random_bytes_user+0x121/0x270 drivers/char/random.c:430
 __do_sys_getrandom drivers/char/random.c:1263 [inline]
 __se_sys_getrandom drivers/char/random.c:1236 [inline]
 __x64_sys_getrandom+0xc4/0x190 drivers/char/random.c:1236
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x000000000000006f -> 0x0000000000000070

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 19562 Comm: syz-executor.4 Not tainted 5.19.0-rc8-syzkaller-00017-g39c3c396f813-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
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