------------[ cut here ]------------
Trying to write to read-only block-device nullb0 (partno 0)
WARNING: CPU: 1 PID: 6876 at block/blk-core.c:857 bio_check_ro block/blk-core.c:857 [inline]
WARNING: CPU: 1 PID: 6876 at block/blk-core.c:857 submit_bio_checks+0x1aba/0x1f70 block/blk-core.c:985
Modules linked in:
CPU: 1 PID: 6876 Comm: syz-executor299 Not tainted 5.9.0-rc1-next-20200821-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:bio_check_ro block/blk-core.c:857 [inline]
RIP: 0010:submit_bio_checks+0x1aba/0x1f70 block/blk-core.c:985
Code: 04 00 00 45 8b a4 24 a4 05 00 00 48 8d 74 24 68 48 89 ef e8 f8 21 fe ff 48 c7 c7 80 47 92 88 48 89 c6 44 89 e2 e8 51 ed bd fd <0f> 0b 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 80 3c 02
RSP: 0018:ffffc900016270f0 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff8880a0436080 RCX: 0000000000000000
RDX: ffff8880a80e2180 RSI: ffffffff815da447 RDI: fffff520002c4e10
RBP: ffff88809efef340 R08: 0000000000000001 R09: ffff8880ae7318a7
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff88809efef348 R14: 0000000000000000 R15: ffff88809efef368
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000180 CR3: 0000000009a8d000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 submit_bio_noacct+0x89/0x12b0 block/blk-core.c:1197
 submit_bio+0x263/0x5b0 block/blk-core.c:1282
 submit_bh_wbc+0x685/0x8e0 fs/buffer.c:3107
 __block_write_full_page+0x837/0x12e0 fs/buffer.c:1847
 block_write_full_page+0x214/0x270 fs/buffer.c:3033
 __writepage+0x60/0x170 mm/page-writeback.c:2311
 write_cache_pages+0x736/0x11b0 mm/page-writeback.c:2246
 generic_writepages mm/page-writeback.c:2337 [inline]
 generic_writepages+0xe2/0x150 mm/page-writeback.c:2326
 do_writepages+0xec/0x290 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x2a1/0x380 mm/filemap.c:422
 filemap_write_and_wait_range mm/filemap.c:655 [inline]
 filemap_write_and_wait_range+0xe1/0x1c0 mm/filemap.c:649
 filemap_write_and_wait include/linux/fs.h:2627 [inline]
 __sync_blockdev fs/block_dev.c:480 [inline]
 sync_blockdev fs/block_dev.c:489 [inline]
 __blkdev_put+0x69a/0x890 fs/block_dev.c:1769
 blkdev_close+0x8c/0xb0 fs/block_dev.c:1853
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:141
 exit_task_work include/linux/task_work.h:25 [inline]
 do_exit+0xb7d/0x29f0 kernel/exit.c:806
 do_group_exit+0x125/0x310 kernel/exit.c:903
 get_signal+0x428/0x1f00 kernel/signal.c:2757
 arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:135 [inline]
 exit_to_user_mode_prepare+0x15d/0x1c0 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x59/0x2b0 kernel/entry/common.c:241
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x445949
Code: Bad RIP value.
RSP: 002b:00007f2125632db8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00000000006dac38 RCX: 0000000000445949
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00000000006dac3c
RBP: 00000000006dac30 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000004 R11: 0000000000000246 R12: 00000000006dac3c
R13: 00007ffe62415d0f R14: 00007f21256339c0 R15: 20c49ba5e353f7cf