Re: [PATCH][RESEND] PIE randomization

[Rik van Riel <riel@redhat.com>]

Chuck Ebbert wrote:
> On 07/04/2007 01:35 PM, Jiri Kosina wrote:
> > On Wed, 4 Jul 2007, Jakub Jelinek wrote:
> >
> > > The above highlighted changes are the cause of random segfaults of PIE 
> > > binaries.  See 
> > > https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=246623 
> > Thanks a lot for pointing this out. Andrew, could this be folded into 
> > pie-randomization.patch please?
> >
> >
> > From: Jiri Kosina <jkosina@suse.cz>
> >
> > pie randomization: fix BAD_ADDR macro
> >
> > pie-randomization.patch makes the load_addr in load_elf_interp() the load 
> > bias of ld.so (difference between the actual load base address and first 
> > PT_LOAD segment's p_vaddr). If the difference equals (on x86) to 
> > 0xfffff000 (which is valid [1]), SIGSEGV is incorrectly sent.
> >
> > This patch changes the BAD_ADDR so that it catches the mappings to the 
> > error-area properly.
>
> But what about this patch that made the opposite change:
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=ce51059be56f63762089412b3ece348067afda85

Ohhh, interesting.

So the original patch has:

#define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)

For some reason(?) it got changed to the clearly buggy:

#define BAD_ADDR(x) ((unsigned long)(x) >= PAGE_MASK)

Jiri's patch undoes that second buggy define, which is very
different from the original that was sent in by you and Ernie.

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