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From Graham Dumpleton <>
Subject Re: Issue with connect() call made in mod_proxy_fdpass?
Date Sun, 01 Jun 2014 07:10:05 GMT
What I don't quite understand is why the Linux manual pages:

are even promoting the style:

  offsetof(struct sockaddr_un, sun_path) + strlen(sun_path) + 1

That would produce a length with is technically 1 greater than what the
size of sockaddr_un can be. I can only imagine that within connect() it
must be deducting 1 for any possible null byte and so allowing the last
byte of sun_path to be a non null byte and never actually checking the last
byte as specified by the length, which would be beyond the valid length of
the structure.

In the Apache code for mod_proxy_fdpass at least it doesn't really matter,
as when copying into sun_path it ensures that the last byte that could ever
be written is the last one possible in sun_path and that will have a null
byte. So there is no risk the Apache code could overrun sun_path.

I expect therefore that the Apache code could have simply used:

  sizeof(struct sockaddr_un)

As for the original issue with mod_proxy_fdpass, that was plain wrong and
on some Linux systems could result in connect() failing with error:

  (22)Invalid argument

as it would regard the supplied length as being over some internal limit it
checks. Doesn't happen on all Linux versions though based on what I have
had reported for some code of my own where I happened to replicate what
mod_proxy_fdpass was doing in that function.


On 1 June 2014 16:56, Christophe JAILLET <>

> Fix in r1598946.
> CJ

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