syzbot

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BUG: KCSAN: data-race in loop_configure / shmem_write_begin

write to 0xffff8881055d7540 of 4 bytes by task 20880 on cpu 0:
 mapping_set_gfp_mask include/linux/pagemap.h:290 [inline]
 loop_configure+0x7f5/0xc30 drivers/block/loop.c:1077
 lo_ioctl+0x641/0x1290
 blkdev_ioctl+0x20e/0x440 block/ioctl.c:614
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:856
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:856
 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 0xffff8881055d7540 of 4 bytes by task 20869 on cpu 1:
 mapping_gfp_mask include/linux/pagemap.h:274 [inline]
 shmem_get_folio mm/shmem.c:2045 [inline]
 shmem_write_begin+0x86/0x1e0 mm/shmem.c:2531
 generic_perform_write+0x1d4/0x3f0 mm/filemap.c:3753
 __generic_file_write_iter+0xe3/0x280 mm/filemap.c:3881
 generic_file_write_iter+0x79/0x1c0 mm/filemap.c:3913
 do_iter_write+0x494/0x750 fs/read_write.c:861
 vfs_writev fs/read_write.c:934 [inline]
 do_pwritev+0x235/0x430 fs/read_write.c:1031
 __do_sys_pwritev fs/read_write.c:1078 [inline]
 __se_sys_pwritev fs/read_write.c:1073 [inline]
 __x64_sys_pwritev+0x54/0x60 fs/read_write.c:1073
 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: 0x00100cca -> 0x00100c0a

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 20869 Comm: syz-executor.5 Not tainted 6.1.0-rc7-syzkaller-00101-g01f856ae6d0c-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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