syzbot

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BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getpage_gfp

read-write to 0xffff888108eaabb0 of 8 bytes by task 12070 on cpu 0:
 shmem_add_to_page_cache+0x802/0x8e0 mm/shmem.c:746
 shmem_getpage_gfp+0x7af/0x1750 mm/shmem.c:1951
 shmem_fault+0xd2/0x350 mm/shmem.c:2128
 __do_fault mm/memory.c:4173 [inline]
 do_shared_fault mm/memory.c:4579 [inline]
 do_fault+0x5df/0xb20 mm/memory.c:4657
 handle_pte_fault mm/memory.c:4917 [inline]
 __handle_mm_fault mm/memory.c:5059 [inline]
 handle_mm_fault+0x889/0xa90 mm/memory.c:5157
 do_user_addr_fault+0x4a1/0x980 arch/x86/mm/fault.c:1407
 handle_page_fault arch/x86/mm/fault.c:1498 [inline]
 exc_page_fault+0x60/0x160 arch/x86/mm/fault.c:1554
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:570
 copy_user_enhanced_fast_string+0xa/0x40 arch/x86/lib/copy_user_64.S:165
 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+0x72/0x90 lib/iov_iter.c:170
 _copy_to_iter+0x261/0x8b0 lib/iov_iter.c:524
 copy_to_iter include/linux/uio.h:176 [inline]
 get_random_bytes_user+0x121/0x270 drivers/char/random.c:430
 __do_sys_getrandom drivers/char/random.c:1280 [inline]
 __se_sys_getrandom drivers/char/random.c:1253 [inline]
 __x64_sys_getrandom+0xc4/0x190 drivers/char/random.c:1253
 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 0xffff888108eaabb0 of 8 bytes by task 12080 on cpu 1:
 shmem_recalc_inode mm/shmem.c:363 [inline]
 shmem_getpage_gfp+0xd8b/0x1750 mm/shmem.c:1961
 shmem_fault+0xd2/0x350 mm/shmem.c:2128
 __do_fault mm/memory.c:4173 [inline]
 do_read_fault mm/memory.c:4524 [inline]
 do_fault+0x500/0xb20 mm/memory.c:4653
 handle_pte_fault mm/memory.c:4917 [inline]
 __handle_mm_fault mm/memory.c:5059 [inline]
 handle_mm_fault+0x889/0xa90 mm/memory.c:5157
 faultin_page mm/gup.c:990 [inline]
 __get_user_pages+0x34a/0xc40 mm/gup.c:1219
 populate_vma_page_range mm/gup.c:1576 [inline]
 __mm_populate+0x26e/0x3a0 mm/gup.c:1689
 mm_populate include/linux/mm.h:2663 [inline]
 vm_mmap_pgoff+0x160/0x1f0 mm/util.c:557
 ksys_mmap_pgoff+0xc2/0x320 mm/mmap.c:1586
 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: 0x000000000000005f -> 0x0000000000000060

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12080 Comm: syz-executor.5 Not tainted 6.0.0-syzkaller-06475-g4c86114194e6-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
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