Date:   Wed, 7 Oct 2020 12:40:01 +0100
From:   Andrew Price <anprice@...hat.com>
To:     syzbot <syzbot+43fa87986bdd31df9de6@...kaller.appspotmail.com>,
        agruenba@...hat.com, cluster-devel@...hat.com,
        linux-kernel@...r.kernel.org, rpeterso@...hat.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [Cluster-devel] general protection fault in gfs2_rgrp_dump

On 06/10/2020 13:48, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    7575fdda Merge tag 'platform-drivers-x86-v5.9-2' of git://..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14abb7c7900000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=de7f697da23057c7
> dashboard link: https://syzkaller.appspot.com/bug?extid=43fa87986bdd31df9de6
> compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+43fa87986bdd31df9de6@...kaller.appspotmail.com
> 
> gfs2: fsid=syz:syz.0: ri_addr = 20
> ri_length = 1
> ri_data0 = 21
> ri_data = 2060
> ri_bitbytes = 0

I could reproduce this by setting ri_bitbytes in the first rindex entry 
to 0. The bug is in the error path.

Patch submitted: 
https://www.redhat.com/archives/cluster-devel/2020-October/msg00008.html

Andy

> start=0 len=0 offset=128
> general protection fault, probably for non-canonical address 0xdffffc0000000020: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000100-0x0000000000000107]
> CPU: 1 PID: 19688 Comm: syz-executor.3 Not tainted 5.9.0-rc8-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:gfs2_rgrp_dump+0x3b/0x6c0 fs/gfs2/rgrp.c:2220
> Code: 24 10 48 89 f3 48 89 7c 24 08 48 bd 00 00 00 00 00 fc ff df e8 06 7a 2b fe 48 89 ea 48 81 c3 00 01 00 00 48 89 d8 48 c1 e8 03 <80> 3c 28 00 74 12 48 89 df e8 97 60 6b fe 48 ba 00 00 00 00 00 fc
> RSP: 0018:ffffc90009037758 EFLAGS: 00010202
> RAX: 0000000000000020 RBX: 0000000000000100 RCX: 0000000000040000
> RDX: dffffc0000000000 RSI: 0000000000016753 RDI: 0000000000016754
> RBP: dffffc0000000000 R08: ffffffff83ddd758 R09: fffff52001206efa
> R10: fffff52001206efa R11: 0000000000000000 R12: ffffffff89364b22
> R13: ffff888042e74000 R14: dffffc0000000000 R15: ffffffff89364943
> FS:  00007fb8f261d700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000016a9e60 CR3: 00000000959d9000 CR4: 00000000001506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   gfs2_consist_rgrpd_i+0xa1/0x110 fs/gfs2/util.c:422
>   compute_bitstructs fs/gfs2/rgrp.c:812 [inline]
>   read_rindex_entry fs/gfs2/rgrp.c:909 [inline]
>   gfs2_ri_update+0xb60/0x1860 fs/gfs2/rgrp.c:986
>   gfs2_rindex_update+0x283/0x320 fs/gfs2/rgrp.c:1032
>   init_inodes fs/gfs2/ops_fstype.c:792 [inline]
>   gfs2_fill_super+0x28e7/0x3fe0 fs/gfs2/ops_fstype.c:1125
>   get_tree_bdev+0x3e9/0x5f0 fs/super.c:1342
>   gfs2_get_tree+0x4c/0x1f0 fs/gfs2/ops_fstype.c:1201
>   vfs_get_tree+0x88/0x270 fs/super.c:1547
>   do_new_mount fs/namespace.c:2875 [inline]
>   path_mount+0x179d/0x29e0 fs/namespace.c:3192
>   do_mount fs/namespace.c:3205 [inline]
>   __do_sys_mount fs/namespace.c:3413 [inline]
>   __se_sys_mount+0x126/0x180 fs/namespace.c:3390
>   do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x46087a
> Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 ad 89 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 8a 89 fb ff c3 66 0f 1f 84 00 00 00 00 00
> RSP: 002b:00007fb8f261ca88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 00007fb8f261cb20 RCX: 000000000046087a
> RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007fb8f261cae0
> RBP: 00007fb8f261cae0 R08: 00007fb8f261cb20 R09: 0000000020000000
> R10: 0000000000000000 R11: 0000000000000202 R12: 0000000020000000
> R13: 0000000020000100 R14: 0000000020000200 R15: 0000000020047a20
> Modules linked in:
> ---[ end trace 8711b33583174bc7 ]---
> RIP: 0010:gfs2_rgrp_dump+0x3b/0x6c0 fs/gfs2/rgrp.c:2220
> Code: 24 10 48 89 f3 48 89 7c 24 08 48 bd 00 00 00 00 00 fc ff df e8 06 7a 2b fe 48 89 ea 48 81 c3 00 01 00 00 48 89 d8 48 c1 e8 03 <80> 3c 28 00 74 12 48 89 df e8 97 60 6b fe 48 ba 00 00 00 00 00 fc
> RSP: 0018:ffffc90009037758 EFLAGS: 00010202
> RAX: 0000000000000020 RBX: 0000000000000100 RCX: 0000000000040000
> RDX: dffffc0000000000 RSI: 0000000000016753 RDI: 0000000000016754
> RBP: dffffc0000000000 R08: ffffffff83ddd758 R09: fffff52001206efa
> R10: fffff52001206efa R11: 0000000000000000 R12: ffffffff89364b22
> R13: ffff888042e74000 R14: dffffc0000000000 R15: ffffffff89364943
> FS:  00007fb8f261d700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000016a9e60 CR3: 00000000959d9000 CR4: 00000000001506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
> 
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