linux-kernel - Re: Is PIE randomization breaking klibc binaries?

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Date:	Thu, 2 Aug 2007 21:10:31 +0200
From:	Ulrich Kunitz <kune@...ne-taler.de>
To:	Sergey Vlasov <vsu@...linux.ru>
Cc:	Chuck Ebbert <cebbert@...hat.com>, linux-kernel@...r.kernel.org,
	honza@...os.cz, jkosina@...e.cz, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: Is PIE randomization breaking klibc binaries?

Sergey Vlasov wrote:

> On Wed, 25 Jul 2007 08:32:43 +0200 Ulrich Kunitz wrote:
> 
> [...]
> > Here is some output from objdump:
> >
> > $ objdump -x bin/sleep
> >
> > bin/sleep:     file format elf64-x86-64
> > bin/sleep
> > architecture: i386:x86-64, flags 0x00000102:
> > EXEC_P, D_PAGED
> > start address 0x000000000040014c
> >
> > Program Header:
> >     PHDR off    0x0000000000000040 vaddr 0x0000000000400040 paddr 0x0000000000400040 align 2**3
> >          filesz 0x00000000000000e0 memsz 0x00000000000000e0 flags r-x
> >   INTERP off    0x0000000000000120 vaddr 0x0000000000400120 paddr 0x0000000000400120 align 2**0
> >          filesz 0x000000000000002a memsz 0x000000000000002a flags r--
> >     LOAD off    0x0000000000000000 vaddr 0x0000000000400000 paddr 0x0000000000400000 align 2**21
> >          filesz 0x00000000000001c3 memsz 0x00000000000001c3 flags r-x
> >    STACK off    0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**3
> >          filesz 0x0000000000000000 memsz 0x0000000000000000 flags rwx
> >
> > Sections:
> > Idx Name          Size      VMA               LMA               File off  Algn
> >   0 .interp       0000002a  0000000000400120  0000000000400120  00000120  2**0
> >                   CONTENTS, ALLOC, LOAD, READONLY, DATA
> >   1 .text         00000059  000000000040014c  000000000040014c  0000014c  2**2
> >                   CONTENTS, ALLOC, LOAD, READONLY, CODE
> >   2 .rodata       0000001e  00000000004001a5  00000000004001a5  000001a5  2**0
> >                   CONTENTS, ALLOC, LOAD, READONLY, DATA
> >   3 .gnu_debuglink 0000000c  0000000000000000  0000000000000000  000001c3  2**0
> >                   CONTENTS, READONLY
> > SYMBOL TABLE:
> > no symbols
> >
> >
> > $ objdump -x lib/klibc-7q-hWrI8UIRMp59zIo378Yl2X7A.so
> 
>. What version of klibc is this?

I think you found it: 1.4.30-3ubuntu2. 

> 
> >
> > lib/klibc-7q-hWrI8UIRMp59zIo378Yl2X7A.so:     file format elf64-x86-64
> > lib/klibc-7q-hWrI8UIRMp59zIo378Yl2X7A.so
> > architecture: i386:x86-64, flags 0x00000102:
> > EXEC_P, D_PAGED
> > start address 0x0000000000200200
> >
> > Program Header:
> >     LOAD off    0x0000000000000000 vaddr 0x0000000000200000 paddr 0x0000000000200000 align 2**21
> >          filesz 0x000000000001197e memsz 0x000000000001197e flags r-x
> >     LOAD off    0x0000000000011980 vaddr 0x0000000000411980 paddr 0x0000000000411980 align 2**21
> 
> Note that the vaddr here can overlap the binary which is linked starting
> at 0x400000.
> 
> This is the bug which I have found and fixed some time ago:
> 
> http://git.kernel.org/?p=libs/klibc/klibc.git;a=commit;h=10df6dfb13ffefe716f12136bbc667f18ff64744
> 
> The fix was included in klibc-1.4.35, but does not seem to be applied in
> your case (the alignment is still 2**21 - it should be 2**20) - so
> either you are using an old klibc, or the "-z max-page-size=0x100000"
> option does not take effect for some reason.
> 
> In my case the buggy klibc worked fine with a stock 2.6.18 kernel, but
> broke when the execshield patch was applied - and the commit 60bfba7e
> code comes from execshield, so it looks like the same problem.
> 
> >          filesz 0x0000000000000100 memsz 0x0000000000004288 flags rw-
> >    STACK off    0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**3
> >          filesz 0x0000000000000000 memsz 0x0000000000000000 flags rwx
> >
> > Sections:
> > Idx Name          Size      VMA               LMA               File off  Algn
> >   0 .text         0000da94  0000000000200200  0000000000200200  00000200  2**2
> >                   CONTENTS, ALLOC, LOAD, READONLY, CODE
> >   1 .rodata       00003cde  000000000020dca0  000000000020dca0  0000dca0  2**5
> >                   CONTENTS, ALLOC, LOAD, READONLY, DATA
> >   2 .data         00000100  0000000000411980  0000000000411980  00011980  2**5
> >                   CONTENTS, ALLOC, LOAD, DATA
> >   3 .bss          00004188  0000000000411a80  0000000000411a80  00011a80  2**5
> >                   ALLOC
> >   4 .gnu_debuglink 0000002c  0000000000000000  0000000000000000  00011a80  2**0
> >                   CONTENTS, READONLY
> > SYMBOL TABLE:
> > no symbols
> >

-- 
Uli Kunitz
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