bisecting fixing commit since 10b84daddbec72c6b440216a69de9a9605127f7a
building syzkaller on 0174c6c8f78a3fdd002a73a5fdf559c1b0ec8c34
testing commit 10b84daddbec72c6b440216a69de9a9605127f7a with gcc (GCC) 8.1.0
kernel signature: 677f2c48b5cd944d1f20b82155fbfe921ec25abb7d91b720debb9bd2aac8ff7b
all runs: crashed: general protection fault in hfs_find_init
testing current HEAD 71c061d2443814de15e177489d5cc00a4a253ef3
testing commit 71c061d2443814de15e177489d5cc00a4a253ef3 with gcc (GCC) 8.1.0
kernel signature: cd93a4bf950d1622a1fbf201cc8418b36b7ba9a0f118fb252c7f8ed29ab6773e
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in hfs_find_init
revisions tested: 2, total time: 15m16.274683314s (build: 9m7.406411761s, test: 5m25.011105572s)
the crash still happens on HEAD
commit msg: Merge tag 'for-5.11-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
crash: BUG: unable to handle kernel NULL pointer dereference in hfs_find_init
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
loop3: detected capacity change from 8192 to 0
hfs: unable to locate alternate MDB
hfs: continuing without an alternate MDB
BUG: kernel NULL pointer dereference, address: 0000000000000040
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 110914067 P4D 110914067 PUD 110915067 PMD 0 
Oops: 0000 [#1] SMP
CPU: 0 PID: 3764 Comm: syz-executor3 Not tainted 5.11.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:hfs_find_init+0x19/0x60 fs/hfs/bfind.c:21
Code: fe ff ff ff eb 8d cc cc cc cc cc cc cc cc cc cc cc 55 48 89 e5 41 54 49 89 f4 53 48 89 fb 48 89 7e 10 48 c7 46 18 00 00 00 00 <8b> 47 40 be c0 0c 00 00 8d 7c 00 04 e8 16 4b e0 ff 48 85 c0 74 23
RSP: 0018:ffffc90000397998 EFLAGS: 00010246
RAX: ffff88810efce800 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffc900003979b8 RDI: 0000000000000000
RBP: ffffc900003979a8 R08: ffffffff84ff2698 R09: 6cfe189d1f56bee0
R10: ffffc90000397a10 R11: 0000000000000286 R12: ffffc900003979b8
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88810e0355e8
FS:  00007f0cbd9c6700(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000040 CR3: 0000000110913000 CR4: 0000000000350ef0
Call Trace:
 hfs_ext_read_extent+0x53/0x1a0 fs/hfs/extent.c:200
 hfs_get_block+0x162/0x220 fs/hfs/extent.c:366
 block_read_full_page+0x119/0x420 fs/buffer.c:2288
 hfs_readpage+0x13/0x20 fs/hfs/inode.c:39
 do_read_cache_page+0x5db/0x780 mm/filemap.c:3097
 read_cache_page+0xd/0x10 mm/filemap.c:3196
 read_mapping_page include/linux/pagemap.h:500 [inline]
 hfs_btree_open+0x136/0x340 fs/hfs/btree.c:78
 hfs_mdb_get+0x4ee/0x610 fs/hfs/mdb.c:199
 hfs_fill_super+0x361/0x630 fs/hfs/super.c:406
 mount_bdev+0x197/0x1d0 fs/super.c:1366
 hfs_mount+0x10/0x20 fs/hfs/super.c:456
 legacy_get_tree+0x2f/0x50 fs/fs_context.c:592
 vfs_get_tree+0x28/0xc0 fs/super.c:1496
 do_new_mount fs/namespace.c:2878 [inline]
 path_mount+0x765/0xaf0 fs/namespace.c:3208
 do_mount+0x77/0x90 fs/namespace.c:3221
 __do_sys_mount fs/namespace.c:3429 [inline]
 __se_sys_mount fs/namespace.c:3406 [inline]
 __x64_sys_mount+0xc0/0xe0 fs/namespace.c:3406
 do_syscall_64+0x37/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x457a7a
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 5d 8f fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 3a 8f fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007f0cbd9c5bb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000020000000 RCX: 0000000000457a7a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f0cbd9c5c00
RBP: 0000000000000003 R08: 00000000200001c0 R09: 0000000020000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000000000666 R14: 00000000006fba30 R15: 0000000000000000
Modules linked in:
CR2: 0000000000000040
---[ end trace c06ac782aa9397b5 ]---
RIP: 0010:hfs_find_init+0x19/0x60 fs/hfs/bfind.c:21
Code: fe ff ff ff eb 8d cc cc cc cc cc cc cc cc cc cc cc 55 48 89 e5 41 54 49 89 f4 53 48 89 fb 48 89 7e 10 48 c7 46 18 00 00 00 00 <8b> 47 40 be c0 0c 00 00 8d 7c 00 04 e8 16 4b e0 ff 48 85 c0 74 23
RSP: 0018:ffffc90000397998 EFLAGS: 00010246
RAX: ffff88810efce800 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffc900003979b8 RDI: 0000000000000000
RBP: ffffc900003979a8 R08: ffffffff84ff2698 R09: 6cfe189d1f56bee0
R10: ffffc90000397a10 R11: 0000000000000286 R12: ffffc900003979b8
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88810e0355e8
FS:  00007f0cbd9c6700(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000040 CR3: 0000000110913000 CR4: 0000000000350ef0