netdev - Re: [syzbot] [mptcp?] general protection fault in proc

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Message-ID: <89c2208c-fe23-43eb-89ef-876e55731a50@kernel.org>
Date: Sat, 4 Jan 2025 20:11:49 +0100
From: Matthieu Baerts <matttbe@...nel.org>
To: Al Viro <viro@...iv.linux.org.uk>, Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, geliang@...nel.org, horms@...nel.org,
 kuba@...nel.org, linux-kernel@...r.kernel.org, martineau@...nel.org,
 mptcp@...ts.linux.dev, netdev@...r.kernel.org, pabeni@...hat.com,
 syzkaller-bugs@...glegroups.com,
 syzbot <syzbot+e364f774c6f57f2c86d1@...kaller.appspotmail.com>
Subject: Re: [syzbot] [mptcp?] general protection fault in proc_scheduler

Hi Al, Eric,

On 04/01/2025 20:00, Al Viro wrote:
> On Sat, Jan 04, 2025 at 07:53:22PM +0100, Eric Dumazet wrote:
> 
>> I do think this is a bug in process accounting, not in networking.
>>
>> It might make sense to output a record on a regular file, but probably
>> not on any other files.
>>
>> diff --git a/kernel/acct.c b/kernel/acct.c
>> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
>> 100644
>> --- a/kernel/acct.c
>> +++ b/kernel/acct.c
>> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
>>         const struct cred *orig_cred;
>>         struct file *file = acct->file;
>>
>> +       if (S_ISREG(file_inode(file)->i_mode))
>> +               return;
> 
> ... won't help, since the file in question *is* a regular file.  IOW, it's
> a wrong predicate here.

On my side, it looks like I'm not able to reproduce the issue with this
patch. Without it, it is very easy to reproduce it. (But I don't know if
there are other consequences that would avoid the issue to happen: when
looking at the logs, with the patch, I don't have heaps of "Process
accounting resumed" messages that I had before.)

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.