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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getpage_gfp

write to 0xffff88814c913260 of 8 bytes by task 12476 on cpu 1:
 shmem_add_to_page_cache+0x55d/0x670 mm/shmem.c:742
 shmem_getpage_gfp+0xaf1/0x12c0 mm/shmem.c:1936
 shmem_fault+0xd1/0x3c0 mm/shmem.c:2114
 __do_fault mm/memory.c:3849 [inline]
 do_read_fault mm/memory.c:4164 [inline]
 do_fault mm/memory.c:4293 [inline]
 handle_pte_fault mm/memory.c:4551 [inline]
 __handle_mm_fault mm/memory.c:4686 [inline]
 handle_mm_fault+0xba6/0x1590 mm/memory.c:4784
 do_user_addr_fault+0x609/0xbe0 arch/x86/mm/fault.c:1397
 handle_page_fault arch/x86/mm/fault.c:1485 [inline]
 exc_page_fault+0x91/0x290 arch/x86/mm/fault.c:1541
 asm_exc_page_fault+0x1e/0x30
 copy_user_enhanced_fast_string+0xe/0x30
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_from_user arch/x86/include/asm/uaccess_64.h:52 [inline]
 copyin lib/iov_iter.c:168 [inline]
 _copy_from_iter+0x1ac/0x990 lib/iov_iter.c:767
 copy_from_iter include/linux/uio.h:164 [inline]
 copy_from_iter_full include/linux/uio.h:170 [inline]
 sctp_user_addto_chunk+0x67/0x130 net/sctp/sm_make_chunk.c:1565
 sctp_datamsg_from_user+0x59d/0x9c0 net/sctp/chunk.c:269
 sctp_sendmsg_to_asoc+0x504/0xc00 net/sctp/socket.c:1855
 sctp_sendmsg+0x1296/0x1ad0 net/sctp/socket.c:2027
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:819
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg net/socket.c:724 [inline]
 __sys_sendto+0x21e/0x2c0 net/socket.c:2036
 __do_sys_sendto net/socket.c:2048 [inline]
 __se_sys_sendto net/socket.c:2044 [inline]
 __x64_sys_sendto+0x74/0x90 net/socket.c:2044
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88814c913260 of 8 bytes by task 12488 on cpu 0:
 shmem_recalc_inode mm/shmem.c:363 [inline]
 shmem_getpage_gfp+0xf23/0x12c0 mm/shmem.c:1946
 shmem_fault+0xd1/0x3c0 mm/shmem.c:2114
 __do_fault mm/memory.c:3849 [inline]
 do_read_fault mm/memory.c:4164 [inline]
 do_fault mm/memory.c:4293 [inline]
 handle_pte_fault mm/memory.c:4551 [inline]
 __handle_mm_fault mm/memory.c:4686 [inline]
 handle_mm_fault+0xba6/0x1590 mm/memory.c:4784
 faultin_page mm/gup.c:939 [inline]
 __get_user_pages+0x388/0xc80 mm/gup.c:1160
 populate_vma_page_range mm/gup.c:1492 [inline]
 __mm_populate+0x24d/0x370 mm/gup.c:1601
 mm_populate include/linux/mm.h:2734 [inline]
 vm_mmap_pgoff+0x160/0x1f0 mm/util.c:524
 ksys_mmap_pgoff+0xc2/0x320 mm/mmap.c:1623
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000000329 -> 0x000000000000032a

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12488 Comm: syz-executor.3 Not tainted 5.16.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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