Re: [PATCH v2 0/3] posix: Execute file function fixes

[Paul Eggert <eggert at cs dot ucla dot edu>]

On 02/19/2016 12:19 PM, Adhemerval Zanella wrote:
> And it is a regression only if you consider dynamic allocation an alternative,

It's a regression in that it would break some applications that 
currently work. An application that is simple (no signal handling, 
single-threaded, etc.) can invoke programs with many arguments now, but 
the same application won't work if that patch is installed.

Come to think of it, execlp, posix_spawn, and posix_spawnp can all use 
malloc, since POSIX does not require them to be async-signal-safe. So 
you can go back to using malloc for their implementations, when they are 
given large argument vectors. The only conformance problem here will be 
execl and execle.

For these two, I suggest a machine-dependent implementation, with the 
default being something along the lines of the attached (this is totally 
untested, I'm just trying to give the gist).

> A better strategy would be set either hard limits on stack usage in design phase or to focus on enable GLIBC to use a better stack protection mechanism (preferable through compiler assistance).

The latter sounds like a good idea, but is a bigger project and I doubt 
whether we'd want to wait for that project to be finished before fixing 
the exec-family problems in question.

Attachment: execl.c
Description: Text document