syzbot

loop0: detected capacity change from 0 to 544
==================================================================
BUG: KCSAN: data-race in ext4_fill_super / iov_iter_copy_from_user_atomic

write to 0xffff88812c649000 of 4096 bytes by task 5535 on cpu 1:
 instrument_copy_from_user include/linux/instrumented.h:136 [inline]
 copyin lib/iov_iter.c:200 [inline]
 iov_iter_copy_from_user_atomic+0x2e5/0xb60 lib/iov_iter.c:1053
 generic_perform_write+0x1e4/0x3a0 mm/filemap.c:3668
 __generic_file_write_iter+0x202/0x300 mm/filemap.c:3757
 blkdev_write_iter+0x1ea/0x2b0 fs/block_dev.c:1705
 call_write_iter include/linux/fs.h:2114 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812c649404 of 4 bytes by task 5532 on cpu 0:
 ext4_blocks_count fs/ext4/ext4.h:3228 [inline]
 ext4_fill_super+0x2b70/0x8010 fs/ext4/super.c:4605
 mount_bdev+0x1e8/0x290 fs/super.c:1368
 ext4_mount+0x2d/0x40 fs/ext4/super.c:6632
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4a/0x1a0 fs/super.c:1498
 do_new_mount fs/namespace.c:2905 [inline]
 path_mount+0x11d4/0x1ce0 fs/namespace.c:3235
 do_mount fs/namespace.c:3248 [inline]
 __do_sys_mount fs/namespace.c:3456 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3433
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3433
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5532 Comm: syz-executor.0 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
EXT4-fs (loop0): bad geometry: first data block 0 is beyond end of filesystem (0)
loop0: detected capacity change from 0 to 544
EXT4-fs (loop0): VFS: Can't find ext4 filesystem