BUG: unable to handle kernel NULL pointer dereference in gfs2_evict_inode

[Wei Chen]

Dear Linux Developer,

Recently when using our tool to fuzz kernel, the following crash was triggered:

HEAD commit: 64570fbc14f8 Linux 5.15-rc5
git tree: upstream
compiler: gcc 8.0.1
console output:
https://drive.google.com/file/d/1yppAEEN16x0lR3fd5t-NQ1itCoKLFtfP/view?usp=share_link
kernel config: https://drive.google.com/file/d/1uDOeEYgJDcLiSOrx9W8v2bqZ6uOA_55t/view?usp=share_link

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: Wei Chen <harperchen1110@xxxxxxxxx>

RBP: 0000000020000000 R08: 00007f39b7fa3af0 R09: 0000000020000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000020000100
R13: 00007f39b7fa3ab0 R14: 0000000000000001 R15: 0000000020047a20
gfs2: fsid=syz:syz.0: can't lookup journal index: 0
BUG: kernel NULL pointer dereference, address: 000000000000008c
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD c1e1067 P4D c1e1067 PUD 1a9e8067 PMD 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 0 PID: 11045 Comm: syz-executor.0 Not tainted 5.15.0-rc5 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.13.0-48-gd9c812dda519-prebuilt.qemu.org 04/01/2014
RIP: 0010:gfs2_evict_inode+0x47b/0xb00
Code: 3b 14 ff be 01 00 00 00 48 89 df e8 af 6f 44 ff 48 8b bb b8 04
00 00 31 f6 e8 e1 47 fd ff 49 8b 87 00 09 00 00 31 f6 4c 89 ff <8b> 90
8c 00 00 00 e8 ba 4a 00 00 31 ff 41 89 c5 89 c6 e8 ae 3c 14
RSP: 0018:ffffc9000df7fb10 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888016648d10 RCX: 0000000000040000
RDX: ffffc900013d5000 RSI: 0000000000000000 RDI: ffff88801a800000
RBP: ffffc9000df7fbc0 R08: ffffffff8229378f R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: ffff888016648f38
R13: 0000000000000000 R14: ffff88801a800000 R15: ffff88801a800000
FS:  00007f39b7fa4700(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000000008c CR3: 0000000017567000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 evict+0x11c/0x230
 iput+0x2e9/0x500
 dentry_unlink_inode+0x111/0x1a0
 __dentry_kill+0x186/0x280
 dput.part.32+0x60d/0x940
 gfs2_fill_super+0x8c1/0x10f0
 get_tree_bdev+0x243/0x340
 gfs2_get_tree+0x24/0xd0
 vfs_get_tree+0x29/0x100
 path_mount+0x58e/0x10a0
 do_mount+0x9b/0xb0
 __x64_sys_mount+0x13a/0x150
 do_syscall_64+0x34/0xb0
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x46abda
Code: 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f
84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d
01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f39b7fa3a48 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f39b7fa3af0 RCX: 000000000046abda
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f39b7fa3ab0
RBP: 0000000020000000 R08: 00007f39b7fa3af0 R09: 0000000020000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000020000100
R13: 00007f39b7fa3ab0 R14: 0000000000000001 R15: 0000000020047a20
Modules linked in:
CR2: 000000000000008c
---[ end trace 194497c38992c5b1 ]---
RIP: 0010:gfs2_evict_inode+0x47b/0xb00
Code: 3b 14 ff be 01 00 00 00 48 89 df e8 af 6f 44 ff 48 8b bb b8 04
00 00 31 f6 e8 e1 47 fd ff 49 8b 87 00 09 00 00 31 f6 4c 89 ff <8b> 90
8c 00 00 00 e8 ba 4a 00 00 31 ff 41 89 c5 89 c6 e8 ae 3c 14
RSP: 0018:ffffc9000df7fb10 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888016648d10 RCX: 0000000000040000
RDX: ffffc900013d5000 RSI: 0000000000000000 RDI: ffff88801a800000
RBP: ffffc9000df7fbc0 R08: ffffffff8229378f R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: ffff888016648f38
R13: 0000000000000000 R14: ffff88801a800000 R15: ffff88801a800000
FS:  00007f39b7fa4700(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000000008c CR3: 0000000017567000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0: 3b 14 ff              cmp    (%rdi,%rdi,8),%edx
   3: be 01 00 00 00        mov    $0x1,%esi
   8: 48 89 df              mov    %rbx,%rdi
   b: e8 af 6f 44 ff        callq  0xff446fbf
  10: 48 8b bb b8 04 00 00 mov    0x4b8(%rbx),%rdi
  17: 31 f6                xor    %esi,%esi
  19: e8 e1 47 fd ff        callq  0xfffd47ff
  1e: 49 8b 87 00 09 00 00 mov    0x900(%r15),%rax
  25: 31 f6                xor    %esi,%esi
  27: 4c 89 ff              mov    %r15,%rdi
* 2a: 8b 90 8c 00 00 00    mov    0x8c(%rax),%edx <-- trapping instruction
  30: e8 ba 4a 00 00        callq  0x4aef
  35: 31 ff                xor    %edi,%edi
  37: 41 89 c5              mov    %eax,%r13d
  3a: 89 c6                mov    %eax,%esi
  3c: e8                    .byte 0xe8
  3d: ae                    scas   %es:(%rdi),%al
  3e: 3c 14                cmp    $0x14,%al

Best,
Wei