syzbot

loop3: detected capacity change from 0 to 264192
==================================================================
BUG: KCSAN: data-race in shmem_getattr / shmem_getpage_gfp

write to 0xffff88813455e5b0 of 8 bytes by task 43 on cpu 0:
 shmem_getpage_gfp+0xe88/0x12c0 mm/shmem.c:1944
 shmem_getpage mm/shmem.c:150 [inline]
 shmem_file_read_iter+0x1b2/0x5d0 mm/shmem.c:2555
 call_read_iter include/linux/fs.h:2156 [inline]
 do_iter_readv_writev+0x2fb/0x380 fs/read_write.c:723
 do_iter_read+0x192/0x5d0 fs/read_write.c:786
 vfs_iter_read+0x4c/0x70 fs/read_write.c:828
 lo_read_simple drivers/block/loop.c:284 [inline]
 do_req_filebacked drivers/block/loop.c:499 [inline]
 loop_handle_cmd drivers/block/loop.c:1857 [inline]
 loop_process_work+0x70b/0x1280 drivers/block/loop.c:1897
 loop_rootcg_workfn+0x1b/0x20 drivers/block/loop.c:1928
 process_one_work+0x3fc/0x980 kernel/workqueue.c:2298
 worker_thread+0x616/0xa70 kernel/workqueue.c:2445
 kthread+0x2c7/0x2e0 kernel/kthread.c:327
 ret_from_fork+0x1f/0x30

read to 0xffff88813455e5b0 of 8 bytes by task 2451 on cpu 1:
 shmem_getattr+0x40/0x240 mm/shmem.c:1068
 vfs_getattr_nosec+0x153/0x2f0 fs/stat.c:123
 vfs_getattr+0x4d/0x60 fs/stat.c:160
 loop_get_status+0x162/0x240 drivers/block/loop.c:1341
 loop_get_status64 drivers/block/loop.c:1433 [inline]
 lo_ioctl+0x1eb/0x1270 drivers/block/loop.c:1578
 blkdev_ioctl+0x20e/0x440 block/ioctl.c:597
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:860
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:860
 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: 0x00000000000000ae -> 0x00000000000000b1

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2451 Comm: syz-executor.3 Not tainted 5.15.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
 loop3: p1 < > p2 < > p3 p4 < p5 >
loop3: p3 size 1912633224 extends beyond EOD, truncated
loop3: p5 size 1912633224 extends beyond EOD, truncated