Re: Executing shell code on the signal stack, or why is this is a bad idea

[Chet Ramey]

On 6/6/13 5:31 AM, Lionel Cons wrote:
> On 6 June 2013 11:29, Lionel Cons <lionelcons1972@googlemail.com> wrote:
>> Forwarding an interesting posting from Roland Mainz who did an
>> investigation why signal trap processing in ksh93, bash and dash is
>> currently not reliable.
>>
>> Lionel
>>
> 
> PS: malloc() from AT&T libast, used by ksh93, is async signal safe.
> Unless bash's sh_malloc() has a similar functionality you'll need a
> different solution, such as using signalfd()

The internal bash malloc (lib/malloc/malloc.c) blocks signals, but it's
easy to compile bash without it, and many malloc implementations (e.g.,
the Linux libc malloc) do not do signal manipulation.

I did a lot of work between bash-4.2 and bash-4.3, currently in alpha
testing, to move any execution of non-signal-safe functions and code out
of signal handlers.

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