[syslinux] [PATCH 0/2] Stack overflows when running commands

[Celelibi]

2016-01-09 17:05 UTC+01:00, Gene Cumm <gene.cumm at gmail.com>:
> On Tue, Oct 13, 2015 at 12:04 AM, celelibi--- via Syslinux
> <syslinux at zytor.com> wrote:
>> From: Sylvain Gault <sylvain.gault at gmail.com>
>>
>> Hello there,
>>
>> I propose 2 patches that fix two possible stack overflows either when
>> running a
>> COM32 module or when loading a new config file.
>>
>> I didn't find a better way to do this than to use the infamous
>> setjmp/longjmp
>> functions to restore the stack to a previous state. This makes the logic a
>> bit
>> more complex, but the behavior is not changed.
>
> The other way to do this is set variable(s) about the next target
> state and then return from the functions.  I'm not sure which is the
> better way, however.

That would change the semantics of the execute() function which is
supposed to never return. So all the modules using that function
directly or indirectly would need to be patched.

Are there some people who wrote their own modules? If so, Ady would
yell at us as a backward compatibility guardian. ^^

But I agree that would allow the modules to clean up after themselves:
Freeing memory and closing files. But maybe a generic resource
tracking is better anyway.

>
>> Although these bugs are not very visible right now because of some
>> useless
>> section in the binaries taking some space allowing the stack to overflow
>> without consequences, they might need to be fixed very soon.
>>
>> Still remain a limitation when running a lot of commands (or loading lots
>> of
>> time some config file) is that some files might not be closed and some
>> memory
>> may not be freed.
>>
>> Sylvain Gault (2):
>>   ldlinux: fix stack overflow when running COM32 modules
>>   core: Fix stack overflow when reloading config
>>
>>  com32/elflink/ldlinux/execute.c |  4 ++-
>>  com32/elflink/ldlinux/ldlinux.c | 28 ++++++++++++++------
>>  core/elflink/load_env32.c       | 58
>> ++++++++++++++++++++++++++++++++++++++++-
>>  3 files changed, 80 insertions(+), 10 deletions(-)
>
>
> --
> -Gene
>


Celelibi