Messages in this thread | | | Date | Mon, 7 Mar 2016 15:16:21 -0800 | Subject | Re: [PATCH v3 07/19] x86, kaslr: Get correct max_addr for relocs pointer | From | Kees Cook <> |
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On Fri, Mar 4, 2016 at 8:25 AM, Baoquan He <bhe@redhat.com> wrote: > From: Yinghai Lu <yinghai@kernel.org> > > There is boundary checking for pointer in kaslr relocation handling. > > Current code is using output_len, and that is VO (vmlinux after objcopy) > file size plus vmlinux.relocs file size. > > That is not right, as we should use loaded address for running.
I think this needs clarification. If I'm understanding correctly, the max_addr check should stop at the end of VO, and not include bss, brk, etc. which follows. In which case, this change is correct: the bounds checking needed to be tightened.
-Kees
> > At that time parse_elf already move the sections according to ELF headers. > > The valid range should be VO [_text, __bss_start) loaded physical addresses. > > In the patch, add export for __bss_start to voffset.h and use it to get > max_addr. > > Signed-off-by: Yinghai Lu <yinghai@kernel.org> > --- > v2->v3: > Tune the patch log. > > arch/x86/boot/compressed/Makefile | 2 +- > arch/x86/boot/compressed/misc.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile > index fef80fa..2e7c0ce 100644 > --- a/arch/x86/boot/compressed/Makefile > +++ b/arch/x86/boot/compressed/Makefile > @@ -41,7 +41,7 @@ LDFLAGS_vmlinux := -T > hostprogs-y := mkpiggy > HOST_EXTRACFLAGS += -I$(srctree)/tools/include > > -sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p' > +sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p' > > quiet_cmd_voffset = VOFFSET $@ > cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@ > diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c > index 069120e..dd7ed8a 100644 > --- a/arch/x86/boot/compressed/misc.c > +++ b/arch/x86/boot/compressed/misc.c > @@ -259,7 +259,7 @@ static void handle_relocations(void *output, unsigned long output_len) > int *reloc; > unsigned long delta, map, ptr; > unsigned long min_addr = (unsigned long)output; > - unsigned long max_addr = min_addr + output_len; > + unsigned long max_addr = min_addr + (VO___bss_start - VO__text); > > /* > * Calculate the delta between where vmlinux was linked to load > -- > 2.5.0 >
-- Kees Cook Chrome OS & Brillo Security
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