BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
PGD 98476067 P4D 98476067 PUD 95b8c067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 30025 Comm: syz-executor.3 Not tainted 4.19.113-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:359 [inline]
RIP: 0010:lock_buffer include/linux/buffer_head.h:365 [inline]
RIP: 0010:alloc_branch fs/minix/itree_common.c:88 [inline]
RIP: 0010:get_block+0x76c/0x1300 fs/minix/itree_common.c:191
Code: 00 00 49 8b bc 24 28 01 00 00 b9 08 00 00 00 e8 fa 42 bc ff 31 d2 be 6c 01 00 00 48 c7 c7 60 48 7c 87 49 89 c4 e8 b4 66 4e ff <f0> 49 0f ba 2c 24 02 40 0f 92 c6 31 ff 40 88 74 24 78 e8 cd 0d 6f
RSP: 0018:ffff888049097788 EFLAGS: 00010246
RAX: 0000000000000007 RBX: ffff888049097888 RCX: 1ffffffff11f89f8
RDX: 0000000000000000 RSI: ffffffff88b92960 RDI: ffff888043828224
RBP: ffff888049097920 R08: ffff888043828200 R09: fffff9400016db07
R10: fffff9400016db06 R11: ffffea0000b6d837 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff88804909784c R15: 0000000000000c98
FS:  00007f5d5df57700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000008c108000 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+0x480/0x17a0 fs/buffer.c:1967
 __block_write_begin fs/buffer.c:2017 [inline]
 block_write_begin+0x58/0x2e0 fs/buffer.c:2076
 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+0x37f/0x729 mm/filemap.c:3315
 call_write_iter include/linux/fs.h:1821 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x512/0x760 fs/read_write.c:487
 vfs_write+0x206/0x550 fs/read_write.c:549
 ksys_write+0x12b/0x2a0 fs/read_write.c:599
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c849
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:00007f5d5df56c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f5d5df576d4 RCX: 000000000045c849
RDX: 0000000008800000 RSI: 0000000020000480 RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000cdc R14: 00000000004cf002 R15: 000000000076bf0c
Modules linked in:
CR2: 0000000000000000
---[ end trace 19ac211936e73ab0 ]---
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:359 [inline]
RIP: 0010:lock_buffer include/linux/buffer_head.h:365 [inline]
RIP: 0010:alloc_branch fs/minix/itree_common.c:88 [inline]
RIP: 0010:get_block+0x76c/0x1300 fs/minix/itree_common.c:191
Code: 00 00 49 8b bc 24 28 01 00 00 b9 08 00 00 00 e8 fa 42 bc ff 31 d2 be 6c 01 00 00 48 c7 c7 60 48 7c 87 49 89 c4 e8 b4 66 4e ff <f0> 49 0f ba 2c 24 02 40 0f 92 c6 31 ff 40 88 74 24 78 e8 cd 0d 6f
minix_free_inode: bit 1 already cleared
RSP: 0018:ffff888049097788 EFLAGS: 00010246
minix_free_inode: bit 1 already cleared
RAX: 0000000000000007 RBX: ffff888049097888 RCX: 1ffffffff11f89f8
RDX: 0000000000000000 RSI: ffffffff88b92960 RDI: ffff888043828224
RBP: ffff888049097920 R08: ffff888043828200 R09: fffff9400016db07
R10: fffff9400016db06 R11: ffffea0000b6d837 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff88804909784c R15: 0000000000000c98
FS:  00007f5d5df57700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000008c108000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400