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Message-ID:
<CWLP265MB4157A01AA054C084992AEDD3BC652@CWLP265MB4157.GBRP265.PROD.OUTLOOK.COM>
Date: Fri, 13 Sep 2024 16:00:52 +0000
From: Kate Deplaix <kit-ty-kate@...look.com>
To: Rich Felker <dalias@...c.org>
CC: "musl@...ts.openwall.com" <musl@...ts.openwall.com>
Subject: Re: [PATCH] Increase NGROUPS_MAX from 32 to 1024
The problem is that NGROUPS_MAX is used in downstream projects, not sysconf(_SC_NGROUPS_MAX). Notoriously one of the main user of musl (Alpine Linux) does not modify this value which makes the whole system break completely if a user happens to be added to more than 32 groups.
Changing every opensource projects that use NGROUPS_MAX to use sysconf(_SC_NGROUPS_MAX) instead doesn't seem like a reasonable answer to me, even if it might be the correct one in theory.
I also really don't understand why you want to support 20+ years old kernel versions (pre 2.6.4) which aren't even POSIX conformant according to your own page: https://wiki.musl-libc.org/supported-platforms. I also don't think it would also break anything on those platforms anyway if a higher value was used. Most uses i've seen use this value to allocate a static array, so aside from a couple more bytes of memory used there isn't much to lose.
Cheers,
Kate
________________________________
From: Rich Felker <dalias@...c.org>
Sent: 13 September 2024 15:47
To: Kate Deplaix <kit-ty-kate@...look.com>
Cc: musl@...ts.openwall.com <musl@...ts.openwall.com>
Subject: Re: [musl] [PATCH] Increase NGROUPS_MAX from 32 to 1024
On Fri, Sep 13, 2024 at 11:45:13AM +0000, Kate Deplaix wrote:
> Hi,
>
> Is there anything i can do to make a fix for this go forward?
What requirements are you still trying to satisfy? 3f49203c55cc made
it so initgroups accepts arbitrarily many groups independent of
NGROUPS_MAX.
My reading of POSIX is that the macro NGROUPS_MAX is a "minimum
maximum" that any instance of the implementation might impose, which
for us I think is the 32 imposed by old Linux.
sysconf(_SC_NGROUPS_MAX) does not yet expose a larger runtime max; is
that what you'd like to see happen?
Source I'm going on:
https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/limits.h.html
under the heading "Runtime Increasable Values".
Rich
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