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Re: Seg fault on "echo ~nosuchuser"

From: Chet Ramey
Subject: Re: Seg fault on "echo ~nosuchuser"
Date: Tue, 2 Jun 2020 08:56:57 -0400
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.8.1

On 6/1/20 7:58 PM, Ángel wrote:
> On 2020-06-01 at 15:12 -0400, Chet Ramey wrote:
>> I finally found a case where 16-byte alignment for memory returned by
>> malloc() is required. But it's only on Linux systems that use systemd.
>> I bet it's trying to marshal arguments for IPC and uses instructions
>> that require 16-byte alignment.
>> Thanks for your help verifying this.
>> Chet
> You mean that with systemd getpwnam() crashes if using a malloc() that
> returns addresses not 16-byte aligned?

Yes, that's what I mean. The only significant change between the bash
version that worked and the one(s) that did not is making the memory
the bash malloc returns 16-byte aligned.

Other systems not using glibc or systemd could not reproduce the issue.

> Cornercase, surely, but it seems like a bug in whatever is assuming such
> alignment. That's not even pointer-size alignment.

If systemd or its support libraries are using copy instructions that
require 16-byte alignment, though it's not documented, it's arguably not
a bug.


``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/

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