netdev - Re: [PATCH v3] net/af_unix: don't create a path for a binded socket

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Message-ID: <CAOJe8K1FPGr-2OgqaWOEz4ZHUONJ-p2yW6Uw-dVjXVurGmDwxA@mail.gmail.com>
Date:   Thu, 3 Dec 2020 11:18:21 +0300
From:   Denis Kirjanov <kda@...ux-powerpc.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [PATCH v3] net/af_unix: don't create a path for a binded socket

On 12/1/20, Jakub Kicinski <kuba@...nel.org> wrote:
> On Tue,  1 Dec 2020 12:33:06 +0300 Denis Kirjanov wrote:
>> in the case of the socket which is bound to an adress
>> there is no sense to create a path in the next attempts
>>
>> here is a program that shows the issue:
>>
>> int main()
>> {
>>     int s;
>>     struct sockaddr_un a;
>>
>>     s = socket(AF_UNIX, SOCK_STREAM, 0);
>>     if (s<0)
>>         perror("socket() failed\n");
>>
>>     printf("First bind()\n");
>>
>>     memset(&a, 0, sizeof(a));
>>     a.sun_family = AF_UNIX;
>>     strncpy(a.sun_path, "/tmp/.first_bind", sizeof(a.sun_path));
>>
>>     if ((bind(s, (const struct sockaddr*) &a, sizeof(a))) == -1)
>>         perror("bind() failed\n");
>>
>>     printf("Second bind()\n");
>>
>>     memset(&a, 0, sizeof(a));
>>     a.sun_family = AF_UNIX;
>>     strncpy(a.sun_path, "/tmp/.first_bind_failed", sizeof(a.sun_path));
>>
>>     if ((bind(s, (const struct sockaddr*) &a, sizeof(a))) == -1)
>>         perror("bind() failed\n");
>> }
>>
>> kda@...S15-SP2:~> ./test
>> First bind()
>> Second bind()
>> bind() failed
>> : Invalid argument
>>
>> kda@...S15-SP2:~> ls -la /tmp/.first_bind
>> .first_bind         .first_bind_failed
>>
>> Signed-off-by: Denis Kirjanov <kda@...ux-powerpc.org>
>
> Is the deadlock fixed by the patch Michal pointed out no longer present?
The thing that I'm not satisfied is that we're holding bindlock during
unix_mknod().
I'll send a next version

>