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 0477e92881850d44910a7e94fc2c46f96faa131f
testing commit 0477e92881850d44910a7e94fc2c46f96faa131f with gcc (GCC) 8.1.0
kernel signature: fba4b92cba65a5eb1f063c1a181bced857a0cd05531438946051c6e79767c9b6
all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in hfs_find_init
revisions tested: 2, total time: 15m30.33883085s (build: 8m37.57937003s, test: 6m2.346973548s)
the crash still happens on HEAD
commit msg: Linux 5.10-rc7
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
IPVS: ftp: loaded support on port[0] = 21
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 10b2ef067 P4D 10b2ef067 PUD 10b2f0067 PMD 0 
Oops: 0000 [#1] SMP
CPU: 0 PID: 3680 Comm: syz-executor3 Not tainted 5.10.0-rc7-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 56 74 e0 ff 48 85 c0 74 23
RSP: 0018:ffffc9000043b9a0 EFLAGS: 00010246
RAX: ffff88810f7f3000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffc9000043b9c0 RDI: 0000000000000000
RBP: ffffc9000043b9b0 R08: ffffffff84fe0ed8 R09: 96342fd6fa1a0571
R10: ffffc9000043ba18 R11: 0000000000000282 R12: ffffc9000043b9c0
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88810ec17348
FS:  00007fe5907ff700(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000040 CR3: 000000010b2f2000 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+0x10b/0x3c0 fs/buffer.c:2288
 hfs_readpage+0x13/0x20 fs/hfs/inode.c:39
 do_read_cache_page+0x5e1/0x790 mm/filemap.c:3017
 read_cache_page+0xd/0x10 mm/filemap.c:3116
 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:1419
 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:1549
 do_new_mount fs/namespace.c:2875 [inline]
 path_mount+0x765/0xaf0 fs/namespace.c:3205
 do_mount+0x77/0x90 fs/namespace.c:3218
 __do_sys_mount fs/namespace.c:3426 [inline]
 __se_sys_mount fs/namespace.c:3403 [inline]
 __x64_sys_mount+0xc0/0xe0 fs/namespace.c:3403
 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:00007fe5907febb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000020000000 RCX: 0000000000457a7a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007fe5907fec00
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 1c325d92128377f4 ]---
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 56 74 e0 ff 48 85 c0 74 23
RSP: 0018:ffffc9000043b9a0 EFLAGS: 00010246
RAX: ffff88810f7f3000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffc9000043b9c0 RDI: 0000000000000000
RBP: ffffc9000043b9b0 R08: ffffffff84fe0ed8 R09: 96342fd6fa1a0571
R10: ffffc9000043ba18 R11: 0000000000000282 R12: ffffc9000043b9c0
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88810ec17348
FS:  00007fe5907ff700(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000040 CR3: 000000010b2f2000 CR4: 0000000000350ef0