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    SubjectRe: Is PIE randomization breaking klibc binaries?
    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?

    >
    > 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
    >
    [unhandled content-type:application/pgp-signature]
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