Re: BASH recursion segfault, FUNCNEST doesn't help

[Ángel]

On 2022-06-02 at 20:00 +0000, Gergely wrote:
> Well, the issue is not the fact that this is a resource exhaustion,
> but rather the fact that it's entirely OS-dependent and the
> programmer has zero control over it.

The programmer could have avoided creating an infinite source file
recursion.

I don't think it would be hard to add a SOURCENEST limit, but I find it
would mostly help to catch programming errors, not as a normal
exceptional case for a valid program that the programmer should be
expecting.
Can you provide an example where a sensible program would need to
source a large chain of files sourcing one another or even recursively 
sourcing themselves?

I cannot think of a good use case for that. Someone might choose to do
"recursive file programming", but that would come with the need to
avoid infinite recursion, somehow.
For a normal programmer which simply has two library functions
requiring one another, a simple "#ifndef X / #define X" pattern is easy
to produce by adding at the top something like
 > if [ "$LIBRARY_FOO_INCLUDED" = 1 ]; then return; fi; 
> LIBRARY_FOO_INCLUDED=1.


A case for a program that needs to create hundreds of files sourcing one 
another.
And there is little you could do to recover other than abruptly
terminating the program. It would just be able to provide a nicer error
message.

I don't think it's even a vulnerability since the number of included
files would need to be controlled by the attacker (but only the
*number* of sourced files, if he also controlled the contents, he would
already be able to execute its own code).
Note that the fact you may get the crash to happen on different
functions doesn't really matter here, since it's really an out of
memory.
You may produce similar results by changing the value of ulimit -s


Regards