Re: Fchown on unix domain sockets?

[Jan Engelhardt]

>> As some manpage might say, the socket thing you see in "ls -l" is just a
>> reference thing. When you connect to it, ls -l /proc/pidofprogram/fd/ does
>> not show the path, but [socket:xxxx] which shows that the filesystem object
>> is not used anymore.
>
>When I connect to it is the point. I want to set the permissions etc so that
>only the progams that are supposed to be talking to it talk to it.

How about setting the permissions beforehand?

>> >I don't mind it not working but I think it should report an error. This is
>> > on 2.6.3 kernel.
>>
>> What would you like it to do? EINVAL like the others or change the actual
>> inode's permission?
>
>I don't mind. I think it's a meaninful thing to want to do, but if you can't
>do it that way, fine, just let me know with some error code.

There is no chmod op in struct proto_ops in include/linux/net.h.
Thus, all socket types should behave the same when fchmod() is used on their
FDs.

To summarize in short, you could only fchmod() a socket if you open()ed it
rather than by socket(), but otoh, open() is denied for sockets. What a
deadlock ;-)

I think it's this line in fs/open.c:
        file = fget(fd);
Since you (AFAIK) can't get a "struct file" from a socketfd.



Jan Engelhardt
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