bisecting fixing commit since 01364dad1d4577e27a57729d41053f661bb8a5b9
building syzkaller on a34e2c332411388ed2b3f6f1a3acdc062feceb79
testing commit 01364dad1d4577e27a57729d41053f661bb8a5b9 with gcc (GCC) 8.1.0
kernel signature: 4ae9522599b0e8033300d259cf87afbb312ff6d90f4a7aa625de933c8947ad3a
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in get_block
testing current HEAD 14b58326976de6ef3998eefec1dd7f8b38b97a75
testing commit 14b58326976de6ef3998eefec1dd7f8b38b97a75 with gcc (GCC) 8.1.0
kernel signature: 71fc356b8c47e66bb84c36b71407495dc476892195ff2aafa0b32dab93e5d398
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in get_block
revisions tested: 2, total time: 26m53.913307312s (build: 18m47.579014913s, test: 6m53.099451485s)
the crash still happens on HEAD
commit msg: Linux 4.14.193
crash: BUG: unable to handle kernel NULL pointer dereference in get_block
MINIX-fs: mounting unchecked file system, running fsck is recommended
MINIX-fs: mounting unchecked file system, running fsck is recommended
minix_free_inode: bit 1 already cleared
minix_free_inode: bit 1 already cleared
MINIX-fs: mounting unchecked file system, running fsck is recommended
BUG: unable to handle kernel NULL pointer dereference at           (null)
MINIX-fs: mounting unchecked file system, running fsck is recommended
IP: test_and_set_bit arch/x86/include/asm/bitops.h:220 [inline]
IP: test_and_set_bit_lock arch/x86/include/asm/bitops.h:234 [inline]
IP: trylock_buffer include/linux/buffer_head.h:367 [inline]
IP: lock_buffer include/linux/buffer_head.h:373 [inline]
IP: alloc_branch fs/minix/itree_common.c:88 [inline]
IP: get_block+0x63d/0x1060 fs/minix/itree_common.c:191
PGD a58f8067 P4D a58f8067 PUD 9f8c4067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 10792 Comm: syz-executor.5 Not tainted 4.14.193-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888085952440 task.stack: ffff88809b7b0000
RIP: 0010:test_and_set_bit arch/x86/include/asm/bitops.h:220 [inline]
RIP: 0010:test_and_set_bit_lock arch/x86/include/asm/bitops.h:234 [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+0x63d/0x1060 fs/minix/itree_common.c:191
RSP: 0018:ffff88809b7b76a0 EFLAGS: 00010282
RAX: 0000000000000007 RBX: ffff88809b7b77b0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff87f84260 RDI: ffff888085952464
RBP: ffff88809b7b7838 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000078 R11: ffff888085952440 R12: ffff88809b7b7754
R13: 0000000000000c98 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007f0212a32700(0000) GS:ffff8880aed00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000008b325000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 V1_minix_get_block+0x9/0x10 fs/minix/itree_v1.c:56
 minix_get_block+0xa7/0x110 fs/minix/inode.c:379
 __block_write_begin_int+0x33c/0x1620 fs/buffer.c:2038
 __block_write_begin fs/buffer.c:2088 [inline]
 block_write_begin+0x48/0x240 fs/buffer.c:2147
 minix_write_begin+0x2f/0xc0 fs/minix/inode.c:415
 generic_perform_write+0x271/0x450 mm/filemap.c:3047
 __generic_file_write_iter+0x201/0x580 mm/filemap.c:3172
 generic_file_write_iter+0x29f/0x650 mm/filemap.c:3200
 call_write_iter include/linux/fs.h:1778 [inline]
 new_sync_write fs/read_write.c:469 [inline]
 __vfs_write+0x413/0x840 fs/read_write.c:482
 vfs_write+0x150/0x4f0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0x100/0x250 fs/read_write.c:582
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45c8c9
RSP: 002b:00007f0212a31c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f0212a326d4 RCX: 000000000045c8c9
RDX: 000000000000fdef RSI: 00000000200002c0 RDI: 0000000000000003
RBP: 000000000076bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000c96 R14: 00000000004cec92 R15: 000000000076bfac
Code: 6a 08 00 00 49 8b be 28 01 00 00 b9 08 00 00 00 e8 79 34 c4 ff 31 d2 be 74 01 00 00 48 c7 c7 e0 de d9 86 49 89 c6 e8 73 49 6b ff <f0> 49 0f ba 2e 02 0f 83 0e fe ff ff 4c 89 f7 e8 1f f6 c3 ff e9 
RIP: test_and_set_bit arch/x86/include/asm/bitops.h:220 [inline] RSP: ffff88809b7b76a0
RIP: test_and_set_bit_lock arch/x86/include/asm/bitops.h:234 [inline] RSP: ffff88809b7b76a0
RIP: trylock_buffer include/linux/buffer_head.h:367 [inline] RSP: ffff88809b7b76a0
RIP: lock_buffer include/linux/buffer_head.h:373 [inline] RSP: ffff88809b7b76a0
RIP: alloc_branch fs/minix/itree_common.c:88 [inline] RSP: ffff88809b7b76a0
RIP: get_block+0x63d/0x1060 fs/minix/itree_common.c:191 RSP: ffff88809b7b76a0
CR2: 0000000000000000
minix_free_inode: bit 1 already cleared
minix_free_inode: bit 1 already cleared
---[ end trace a948645826f7f246 ]---