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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, Jiri Kosina wrote:

> How about the patch below instead? It survives my testing, and I believe
> it handles both cases properly.
>
> Confirmation from the original bug reporter would obviously be a nice
> bonus too :)
>
>
>
>
> 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>

Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>

However I'd suggest a change to deal with style issues:

> 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

What about this instead, saving 3 lines out of 8:

load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
#if defined(CONFIG_X86) || defined(CONFIG_ARM)
if (current->flags & PF_RANDOMIZE)
load_bias = 0;
#endif


?


Nicolas


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