Date:   Fri, 17 Jan 2020 21:02:48 +0100
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     dev.kurt@...dijck-laurijssen.be, mkl@...gutronix.de,
        o.rempel@...gutronix.de
Cc:     syzbot <syzbot+c3ea30e1e2485573f953@...kaller.appspotmail.com>,
        davem@...emloft.net, linux-can@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: general protection fault in can_rx_register

Hi Marc, Oleksij, Kurt,

On 17/01/2020 14.46, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    f5ae2ea6 Fix built-in early-load Intel microcode alignment
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1033df15e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cfbb8fa33f49f9f3
> dashboard link: 
> https://syzkaller.appspot.com/bug?extid=c3ea30e1e2485573f953
> compiler:       clang version 10.0.0 
> (https://github.com/llvm/llvm-project/ 
> c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13204f15e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=138f5db9e00000
> 
> The bug was bisected to:
> 
> commit 9868b5d44f3df9dd75247acd23dddff0a42f79be
> Author: Kurt Van Dijck <dev.kurt@...dijck-laurijssen.be>
> Date:   Mon Oct 8 09:48:33 2018 +0000
> 
>      can: introduce CAN_REQUIRED_SIZE macro
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=129bfdb9e00000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=119bfdb9e00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=169bfdb9e00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+c3ea30e1e2485573f953@...kaller.appspotmail.com
> Fixes: 9868b5d44f3d ("can: introduce CAN_REQUIRED_SIZE macro")
> 
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 9593 Comm: syz-executor302 Not tainted 5.5.0-rc6-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS 
> Google 01/01/2011
> RIP: 0010:hlist_add_head_rcu include/linux/rculist.h:528 [inline]
> RIP: 0010:can_rx_register+0x43b/0x600 net/can/af_can.c:476

include/linux/rculist.h:528 is

struct hlist_node *first = h->first;

which would mean that 'h' must be NULL.

But the h parameter is rcv_list from
rcv_list = can_rcv_list_find(&can_id, &mask, dev_rcv_lists);

Which can not return NULL - at least when dev_rcv_lists is a proper 
pointer to the dev_rcv_lists provided by can_dev_rcv_lists_find().

So either dev->ml_priv is NULL in the case of having a CAN interface 
(here vxcan) or we have not allocated net->can.rx_alldev_list in 
can_pernet_init() properly (which would lead to an -ENOMEM which is 
reported to whom?).

Hm. I'm lost. Any ideas?

Regards,
Oliver


> Code: 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 89 22 8a fa 
> 4c 89 33 4d 89 e5 49 c1 ed 03 48 b8 00 00 00 00 00 fc ff df <41> 80 7c 
> 05 00 00 74 08 4c 89 e7 e8 c5 21 8a fa 4d 8b 34 24 4c 89
> RSP: 0018:ffffc90003e27d00 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: ffff8880a77336c8 RCX: ffff88809306a100
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880a77336c0
> RBP: ffffc90003e27d58 R08: ffffffff87289cd6 R09: fffff520007c4f94
> R10: fffff520007c4f94 R11: 0000000000000000 R12: 0000000000000008
> R13: 0000000000000001 R14: ffff88809fbcf000 R15: ffff8880a7733690
> FS:  00007fb132f26700(0000) GS:ffff8880aec00000(0000) 
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000178f590 CR3: 00000000996d6000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   raw_enable_filters net/can/raw.c:189 [inline]
>   raw_enable_allfilters net/can/raw.c:255 [inline]
>   raw_bind+0x326/0x1230 net/can/raw.c:428
>   __sys_bind+0x2bd/0x3a0 net/socket.c:1649
>   __do_sys_bind net/socket.c:1660 [inline]
>   __se_sys_bind net/socket.c:1658 [inline]
>   __x64_sys_bind+0x7a/0x90 net/socket.c:1658
>   do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x446ba9
> Code: e8 0c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 
> f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 
> f0 ff ff 0f 83 5b 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fb132f25d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
> RAX: ffffffffffffffda RBX: 00000000006dbc88 RCX: 0000000000446ba9
> RDX: 0000000000000008 RSI: 0000000020000180 RDI: 0000000000000003
> RBP: 00000000006dbc80 R08: 00007fb132f26700 R09: 0000000000000000
> R10: 00007fb132f26700 R11: 0000000000000246 R12: 00000000006dbc8c
> R13: 0000000000000000 R14: 0000000000000000 R15: 068500100000003c
> Modules linked in:
> ---[ end trace 0dedabb13ca8e7d7 ]---
> RIP: 0010:hlist_add_head_rcu include/linux/rculist.h:528 [inline]
> RIP: 0010:can_rx_register+0x43b/0x600 net/can/af_can.c:476
> Code: 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 89 22 8a fa 
> 4c 89 33 4d 89 e5 49 c1 ed 03 48 b8 00 00 00 00 00 fc ff df <41> 80 7c 
> 05 00 00 74 08 4c 89 e7 e8 c5 21 8a fa 4d 8b 34 24 4c 89
> RSP: 0018:ffffc90003e27d00 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: ffff8880a77336c8 RCX: ffff88809306a100
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880a77336c0
> RBP: ffffc90003e27d58 R08: ffffffff87289cd6 R09: fffff520007c4f94
> R10: fffff520007c4f94 R11: 0000000000000000 R12: 0000000000000008
> R13: 0000000000000001 R14: ffff88809fbcf000 R15: ffff8880a7733690
> FS:  00007fb132f26700(0000) GS:ffff8880aec00000(0000) 
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000178f590 CR3: 00000000996d6000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
> This bug 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.
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: 
> https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

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