BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 889ff067 P4D 889ff067 PUD 90259067 PMD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 8935 Comm: syz-executor.0 Not tainted 5.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:0x0
Code: Bad RIP value.
RSP: 0018:ffffc90006287b70 EFLAGS: 00010246
RAX: ffffc90006287be8 RBX: ffffffff8866b7e0 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffff8880792d5a20 RDI: ffff888092c215c0
RBP: ffff8880a47be958 R08: 0000000000000000 R09: ffffc90006287bf0
R10: ffffed10148f7c41 R11: 0000000000000000 R12: ffffc90006287dd8
R13: ffff8880a47be200 R14: 0000000000000000 R15: 0000000000000001
FS:  00007f18de3fd700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000090996000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 generic_perform_write+0x23b/0x4e0 mm/filemap.c:3302
 ext4_buffered_write_iter+0x44d/0x5d0 fs/ext4/file.c:270
 ext4_file_write_iter+0x6c1/0x1840 fs/ext4/file.c:491
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write fs/read_write.c:484 [inline]
 __vfs_write+0x54c/0x710 fs/read_write.c:497
 vfs_write+0x274/0x580 fs/read_write.c:559
 ksys_write+0x11b/0x220 fs/read_write.c:612
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45c889
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f18de3fcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f18de3fd6d4 RCX: 000000000045c889
RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000cdc R14: 00000000004cf042 R15: 000000000076bf0c
Modules linked in:
CR2: 0000000000000000
---[ end trace 2eb5940f58fde8e0 ]---
RIP: 0010:0x0
Code: Bad RIP value.
RSP: 0018:ffffc90006287b70 EFLAGS: 00010246
RAX: ffffc90006287be8 RBX: ffffffff8866b7e0 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffff8880792d5a20 RDI: ffff888092c215c0
RBP: ffff8880a47be958 R08: 0000000000000000 R09: ffffc90006287bf0
R10: ffffed10148f7c41 R11: 0000000000000000 R12: ffffc90006287dd8
R13: ffff8880a47be200 R14: 0000000000000000 R15: 0000000000000001
FS:  00007f18de3fd700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f70d16a4020 CR3: 0000000090996000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400