syzbot

RAX: ffffffffffffffda RBX: 00007f848098a6d4 RCX: 00000000004559d9
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000003
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000010000000001 R11: 0000000000000246 R12: 0000000000000004
R13: 000000000000007e R14: 00000000006f4c70 R15: 0000000000000016
BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
PGD 80000001ab0d9067 P4D 80000001ab0d9067 PUD 1c8fba067 PMD 0 
Oops: 0000 [#1] SMP PTI
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 4549 Comm: syz-executor0 Not tainted 4.17.0-rc3+ #92
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:197 [inline]
RIP: 0010:compound_head include/linux/page-flags.h:142 [inline]
RIP: 0010:PageLocked include/linux/page-flags.h:272 [inline]
RIP: 0010:grow_dev_page fs/buffer.c:942 [inline]
RIP: 0010:grow_buffers fs/buffer.c:1009 [inline]
RIP: 0010:__getblk_slow fs/buffer.c:1036 [inline]
RIP: 0010:__getblk_gfp+0x5bf/0x1620 fs/buffer.c:1316
RSP: 0018:ffff88019e72eb58 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000020 RCX: 0000000000000000
RDX: ffff880197574358 RSI: 0000000000000000 RDI: ffffea0000000000
RBP: ffff88019e72eca0 R08: 0000000001080000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff8801db428f50
FS:  00007f848098a700(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000020 CR3: 00000001ad11c000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 sb_getblk include/linux/buffer_head.h:327 [inline]
 ext4_read_block_bitmap_nowait+0x4eb/0x3ec0 fs/ext4/balloc.c:441
 ext4_mb_init_cache+0x7a6/0x2970 fs/ext4/mballoc.c:863
 ext4_mb_init_group+0x792/0xe90 fs/ext4/mballoc.c:1061
 ext4_mb_load_buddy_gfp+0x94e/0x1d00 fs/ext4/mballoc.c:1129
 ext4_mb_load_buddy fs/ext4/mballoc.c:1240 [inline]
 ext4_mb_find_by_goal+0x4b6/0x18a0 fs/ext4/mballoc.c:1835
 ext4_mb_regular_allocator+0x2a6/0x1fb0 fs/ext4/mballoc.c:2117
 ext4_mb_new_blocks+0x4a23/0x5230 fs/ext4/mballoc.c:4557
 ext4_ext_map_blocks+0x6030/0xcd20 fs/ext4/extents.c:4461
 ext4_map_blocks+0x1218/0x2bd0 fs/ext4/inode.c:636
 ext4_alloc_file_blocks+0x6c9/0x1370 fs/ext4/extents.c:4688
 ext4_fallocate+0xe4b/0x3650 fs/ext4/extents.c:4966
 vfs_fallocate+0x9dc/0xde0 fs/open.c:319
 ksys_fallocate fs/open.c:342 [inline]
 __do_sys_fallocate fs/open.c:350 [inline]
 __se_sys_fallocate fs/open.c:348 [inline]
 __x64_sys_fallocate+0x199/0x290 fs/open.c:348
 do_syscall_64+0x154/0x220 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4559d9
RSP: 002b:00007f8480989c68 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f848098a6d4 RCX: 00000000004559d9
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000003
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000010000000001 R11: 0000000000000246 R12: 0000000000000004
R13: 000000000000007e R14: 00000000006f4c70 R15: 0000000000000016
Code: ff ff ff 44 89 e9 e8 31 a0 ad ff 49 89 c6 4c 8b ab 20 03 00 00 8b 83 a8 0f 00 00 89 45 d0 49 8d 5e 20 4d 85 ed 0f 85 31 01 00 00 <4d> 8b 7e 20 48 89 9d e0 fe ff ff 48 89 df e8 9e 41 dc ff 48 8b 
RIP: __read_once_size include/linux/compiler.h:197 [inline] RSP: ffff88019e72eb58
RIP: compound_head include/linux/page-flags.h:142 [inline] RSP: ffff88019e72eb58
RIP: PageLocked include/linux/page-flags.h:272 [inline] RSP: ffff88019e72eb58
RIP: grow_dev_page fs/buffer.c:942 [inline] RSP: ffff88019e72eb58
RIP: grow_buffers fs/buffer.c:1009 [inline] RSP: ffff88019e72eb58
RIP: __getblk_slow fs/buffer.c:1036 [inline] RSP: ffff88019e72eb58
RIP: __getblk_gfp+0x5bf/0x1620 fs/buffer.c:1316 RSP: ffff88019e72eb58
CR2: 0000000000000020
---[ end trace c9b14be29c854b28 ]---