Re: Seg fault on "echo ~nosuchuser"

[Chet Ramey]

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.

Chet

-- 
``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/