BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
PGD 9e416067 P4D 9e416067 PUD 99742067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 27739 Comm: syz-executor.5 Not tainted 4.19.128-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:test_and_set_bit arch/x86/include/asm/bitops.h:209 [inline]
RIP: 0010:test_and_set_bit_lock arch/x86/include/asm/bitops.h:223 [inline]
RIP: 0010:trylock_buffer include/linux/buffer_head.h:367 [inline]
RIP: 0010:lock_buffer include/linux/buffer_head.h:373 [inline]
RIP: 0010:alloc_branch fs/minix/itree_common.c:88 [inline]
RIP: 0010:get_block+0x772/0x1320 fs/minix/itree_common.c:191
Code: 00 00 49 8b bc 24 28 01 00 00 b9 08 00 00 00 e8 a4 c5 bc ff 31 d2 be 74 01 00 00 48 c7 c7 60 3b 7c 87 49 89 c4 e8 8e 16 4e ff <f0> 49 0f ba 2c 24 02 40 0f 92 c6 31 ff 40 88 74 24 78 e8 d7 73 6f
RSP: 0018:ffff8880467bf5e8 EFLAGS: 00010246
RAX: 0000000000000007 RBX: 0000000000000c98 RCX: 1ffffffff11f8958
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff88808e090424
RBP: ffff8880467bf780 R08: ffff88808e090400 R09: fffff94000191347
R10: fffff94000191346 R11: ffffea0000c89a37 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff8880467bf6ac R15: ffff8880467bf6e8
FS:  00007f29f048c700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000091999000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 minix_get_block+0xe5/0x110 fs/minix/inode.c:379
 __block_write_begin_int+0x47d/0x1770 fs/buffer.c:1978
 __block_write_begin fs/buffer.c:2028 [inline]
 block_write_begin+0x58/0x2e0 fs/buffer.c:2087
 minix_write_begin+0x35/0xe0 fs/minix/inode.c:415
 generic_perform_write+0x1f8/0x4d0 mm/filemap.c:3162
 __generic_file_write_iter+0x24c/0x610 mm/filemap.c:3287
 generic_file_write_iter+0x3f4/0x725 mm/filemap.c:3315
 call_write_iter include/linux/fs.h:1821 [inline]
 do_iter_readv_writev+0x50c/0x790 fs/read_write.c:681
 do_iter_write fs/read_write.c:960 [inline]
 do_iter_write+0x185/0x5e0 fs/read_write.c:941
 vfs_writev+0x15f/0x2f0 fs/read_write.c:1005
 do_pwritev+0x1b6/0x270 fs/read_write.c:1094
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45ca59
Code: 0d b7 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 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f29f048bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
RAX: ffffffffffffffda RBX: 00000000004fb5e0 RCX: 000000000045ca59
RDX: 0000000000000002 RSI: 0000000020000340 RDI: 0000000000000004
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000890 R14: 00000000004cb764 R15: 00007f29f048c6d4
Modules linked in:
CR2: 0000000000000000
---[ end trace 5b8936c8cec8f0ac ]---
RIP: 0010:test_and_set_bit arch/x86/include/asm/bitops.h:209 [inline]
RIP: 0010:test_and_set_bit_lock arch/x86/include/asm/bitops.h:223 [inline]
RIP: 0010:trylock_buffer include/linux/buffer_head.h:367 [inline]
RIP: 0010:lock_buffer include/linux/buffer_head.h:373 [inline]
RIP: 0010:alloc_branch fs/minix/itree_common.c:88 [inline]
RIP: 0010:get_block+0x772/0x1320 fs/minix/itree_common.c:191
Code: 00 00 49 8b bc 24 28 01 00 00 b9 08 00 00 00 e8 a4 c5 bc ff 31 d2 be 74 01 00 00 48 c7 c7 60 3b 7c 87 49 89 c4 e8 8e 16 4e ff <f0> 49 0f ba 2c 24 02 40 0f 92 c6 31 ff 40 88 74 24 78 e8 d7 73 6f
RSP: 0018:ffff8880467bf5e8 EFLAGS: 00010246
RAX: 0000000000000007 RBX: 0000000000000c98 RCX: 1ffffffff11f8958
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff88808e090424
RBP: ffff8880467bf780 R08: ffff88808e090400 R09: fffff94000191347
R10: fffff94000191346 R11: ffffea0000c89a37 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff8880467bf6ac R15: ffff8880467bf6e8
FS:  00007f29f048c700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043e290 CR3: 0000000091999000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400