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Re: libsigsegv 2.5: bug in OpenBSD4.0

From: Bruno Haible
Subject: Re: libsigsegv 2.5: bug in OpenBSD4.0
Date: Sun, 20 Jul 2008 22:16:20 +0200
User-agent: KMail/1.5.4

Hi Eric,

> > When using both stackoverflow_install_handler and segv_handler_missing, a
> > SIGSEGV from dereferencing NULL will be wrongly treated as a stack
> > overflow on platforms that use mincore to check if the fault is near the
> > stack.  In stackvma-mincore.c, mincore_is_near_this recognizes that
> > computation of a target address in between the fault and the stack causes
> > overflow, but then it calls is_unmapped(0,0) anyway.  Since the page
> > containing 0 is unmapped, this results in claiming that a fault on NULL is
> > treated as a fault near the stack, and the stack overflow handler is
> > incorrectly invoked.
> On the other hand, it looks like the following patch is better (at any rate, 
> it 
> matches the comments in the file).

Correct. I have applied your patch. - I'm glad the comments were there,
otherwise I would have been very confused at this point.

Many thanks!


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