lkml.org 
[lkml]   [2011]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v2] binfmt_elf: Fix PIE execution with randomization disabled (was Re: [RFC PATCH] binfmt_elf: Fix PIE execution with randomization disabled)
    On Mon, 3 Oct 2011, Andrew Morton wrote:

    > > From: Jiri Kosina <jkosina@suse.cz>
    > > Subject: [PATCH] binfmt_elf: fix PIE execution with randomization disabled
    > >
    > > The case of address space randomization being disabled in runtime through
    > > randomize_va_space sysctl is not treated properly in load_elf_binary(),
    > > resulting in SIGKILL coming at exec() time for certain PIE-linked binaries
    > > in case the randomization has been disabled at runtime prior to calling
    > > exec().
    > >
    > > Handle the randomize_va_space == 0 case the same way as if we were not
    > > supporting .text randomization at all.
    > >
    > > Based on original patch by H.J. Lu <hongjiu.lu@intel.com> and
    > > Josh Boyer <jwboyer@redhat.com>
    > >
    > > Cc: Ingo Molnar <mingo@elte.hu>
    > > Cc: Jiri Kosina <jkosina@suse.cz>
    > > Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
    > > Cc: Russell King <rmk@arm.linux.org.uk>
    > > Signed-off-by: Jiri Kosina <jkosina@suse.cz>
    > > ---
    > > fs/binfmt_elf.c | 5 ++++-
    > > 1 files changed, 4 insertions(+), 1 deletions(-)
    > >
    > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
    > > index dd0fdfc..bb11fe4 100644
    > > --- a/fs/binfmt_elf.c
    > > +++ b/fs/binfmt_elf.c
    > > @@ -795,7 +795,10 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
    > > * might try to exec. This is because the brk will
    > > * follow the loader, and is not movable. */
    > > #if defined(CONFIG_X86) || defined(CONFIG_ARM)
    > > - load_bias = 0;
    > > + if (current->flags & PF_RANDOMIZE)
    > > + load_bias = 0;
    > > + else
    > > + load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
    > > #else
    > > load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
    > > #endif
    >
    > Guys, it took several people several days and 10+ emails to work out
    > what's happening in there, and the first attempt to fix it was buggy.
    > This is all a huuuuge signal that the code is unobvious, hard to
    > understand, hard to maintain.

    It's unfortunately true. Rewriting the ELF binary loader is on my list of
    very-long-term TODOs. It has became quite a monster over decades.

    > Please, let's get a good code comment in there while it's fresh in your
    > minds. So the next person who comes along doesn't have the same amount
    > of difficulty?

    I have to run now, I will resend the patch to you with an explanatory
    comment added in about 8 hours from now.

    Thanks,

    --
    Jiri Kosina
    SUSE Labs


    \
     
     \ /
      Last update: 2011-10-04 00:09    [W:0.022 / U:34.940 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site