linux-kernel - Re: [PATCH][RESEND] PIE randomization

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Date:	Wed, 4 Jul 2007 19:35:17 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Jakub Jelinek <jakub@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kratochvil <honza@...os.cz>, Ingo Molnar <mingo@...e.hu>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RESEND] PIE randomization

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@...e.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.

[1] https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=246623

Reported-by: Jakub Jelinek <jakub@...hat.com>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index da270d1..466477d 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -80,7 +80,7 @@ static struct linux_binfmt elf_format = {
 		.hasvdso	= 1
 };
 
-#define BAD_ADDR(x) ((unsigned long)(x) >= PAGE_MASK)
+#define BAD_ADDR(x) IS_ERR_VALUE(x)
 
 static int set_brk(unsigned long start, unsigned long end)
 {
-
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