| Message ID | 1498154792-49952-3-git-send-email-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
Hi Kees, On 22 June 2017 at 18:06, Kees Cook <keescook@chromium.org> wrote: > Now that explicitly executed loaders are loaded in the mmap region, > position PIE binaries lower in the address space to avoid possible > collisions with mmap or stack regions. For 64-bit, align to 4GB to > allow runtimes to use the entire 32-bit address space for 32-bit > pointers. > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > arch/arm64/include/asm/elf.h | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h > index 5d1700425efe..f742af8f7c42 100644 > --- a/arch/arm64/include/asm/elf.h > +++ b/arch/arm64/include/asm/elf.h > @@ -113,12 +113,13 @@ > #define ELF_EXEC_PAGESIZE PAGE_SIZE > > /* > - * This is the location that an ET_DYN program is loaded if exec'ed. Typical > - * use of this is to invoke "./ld.so someprog" to test out a new version of > - * the loader. We need to make sure that it is out of the way of the program > - * that it will "exec", and that there is sufficient room for the brk. > + * This is the base location for PIE (ET_DYN with INTERP) loads. On > + * 64-bit, this is raised to 4GB to leave the entire 32-bit address > + * space open for things that want to use the area for 32-bit pointers. > */ > -#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3) > +#define ELF_ET_DYN_BASE (test_thread_flag(TIF_32BIT) ? \ > + 0x000400000UL : \ > + 0x100000000UL) > Why are you merging this with the COMPAT definition? > #ifndef __ASSEMBLY__ > > @@ -173,8 +174,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm, > > #ifdef CONFIG_COMPAT > > -#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3) > - > /* AArch32 registers. */ > #define COMPAT_ELF_NGREG 18 > typedef unsigned int compat_elf_greg_t; > -- > 2.7.4 >
On Thu, Jun 22, 2017 at 11:57 PM, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > Hi Kees, > > On 22 June 2017 at 18:06, Kees Cook <keescook@chromium.org> wrote: >> Now that explicitly executed loaders are loaded in the mmap region, >> position PIE binaries lower in the address space to avoid possible >> collisions with mmap or stack regions. For 64-bit, align to 4GB to >> allow runtimes to use the entire 32-bit address space for 32-bit >> pointers. >> >> Signed-off-by: Kees Cook <keescook@chromium.org> >> --- >> arch/arm64/include/asm/elf.h | 13 ++++++------- >> 1 file changed, 6 insertions(+), 7 deletions(-) >> >> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h >> index 5d1700425efe..f742af8f7c42 100644 >> --- a/arch/arm64/include/asm/elf.h >> +++ b/arch/arm64/include/asm/elf.h >> @@ -113,12 +113,13 @@ >> #define ELF_EXEC_PAGESIZE PAGE_SIZE >> >> /* >> - * This is the location that an ET_DYN program is loaded if exec'ed. Typical >> - * use of this is to invoke "./ld.so someprog" to test out a new version of >> - * the loader. We need to make sure that it is out of the way of the program >> - * that it will "exec", and that there is sufficient room for the brk. >> + * This is the base location for PIE (ET_DYN with INTERP) loads. On >> + * 64-bit, this is raised to 4GB to leave the entire 32-bit address >> + * space open for things that want to use the area for 32-bit pointers. >> */ >> -#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3) >> +#define ELF_ET_DYN_BASE (test_thread_flag(TIF_32BIT) ? \ >> + 0x000400000UL : \ >> + 0x100000000UL) >> > > Why are you merging this with the COMPAT definition? It seemed like the right thing to do since a single definition could handle both cases. Is there something I'm overlooking in the arm64 case? -Kees > >> #ifndef __ASSEMBLY__ >> >> @@ -173,8 +174,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm, >> >> #ifdef CONFIG_COMPAT >> >> -#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3) >> - >> /* AArch32 registers. */ >> #define COMPAT_ELF_NGREG 18 >> typedef unsigned int compat_elf_greg_t; >> -- >> 2.7.4 >>
On Fri, Jun 23, 2017 at 6:52 AM, Kees Cook <keescook@chromium.org> wrote: > On Thu, Jun 22, 2017 at 11:57 PM, Ard Biesheuvel > <ard.biesheuvel@linaro.org> wrote: >> Hi Kees, >> >> On 22 June 2017 at 18:06, Kees Cook <keescook@chromium.org> wrote: >>> Now that explicitly executed loaders are loaded in the mmap region, >>> position PIE binaries lower in the address space to avoid possible >>> collisions with mmap or stack regions. For 64-bit, align to 4GB to >>> allow runtimes to use the entire 32-bit address space for 32-bit >>> pointers. >>> >>> Signed-off-by: Kees Cook <keescook@chromium.org> >>> --- >>> arch/arm64/include/asm/elf.h | 13 ++++++------- >>> 1 file changed, 6 insertions(+), 7 deletions(-) >>> >>> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h >>> index 5d1700425efe..f742af8f7c42 100644 >>> --- a/arch/arm64/include/asm/elf.h >>> +++ b/arch/arm64/include/asm/elf.h >>> @@ -113,12 +113,13 @@ >>> #define ELF_EXEC_PAGESIZE PAGE_SIZE >>> >>> /* >>> - * This is the location that an ET_DYN program is loaded if exec'ed. Typical >>> - * use of this is to invoke "./ld.so someprog" to test out a new version of >>> - * the loader. We need to make sure that it is out of the way of the program >>> - * that it will "exec", and that there is sufficient room for the brk. >>> + * This is the base location for PIE (ET_DYN with INTERP) loads. On >>> + * 64-bit, this is raised to 4GB to leave the entire 32-bit address >>> + * space open for things that want to use the area for 32-bit pointers. >>> */ >>> -#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3) >>> +#define ELF_ET_DYN_BASE (test_thread_flag(TIF_32BIT) ? \ >>> + 0x000400000UL : \ >>> + 0x100000000UL) >>> >> >> Why are you merging this with the COMPAT definition? > > It seemed like the right thing to do since a single definition could > handle both cases. Is there something I'm overlooking in the arm64 > case? And like 5 minutes later there was a loud head-slapping noise in my office. Durr, yeah, arm64 doesn't have to deal with a "native 32-bit" mode, so the merge isn't needed. Yes yes, I will split it back up and drop the thread flag test. Thanks! -Kees >>> #ifndef __ASSEMBLY__ >>> >>> @@ -173,8 +174,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm, >>> >>> #ifdef CONFIG_COMPAT >>> >>> -#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3) >>> - >>> /* AArch32 registers. */ >>> #define COMPAT_ELF_NGREG 18 >>> typedef unsigned int compat_elf_greg_t; >>> -- >>> 2.7.4 >>> > > > > -- > Kees Cook > Pixel Security
On 23 June 2017 at 14:02, Kees Cook <keescook@chromium.org> wrote: > On Fri, Jun 23, 2017 at 6:52 AM, Kees Cook <keescook@chromium.org> wrote: >> On Thu, Jun 22, 2017 at 11:57 PM, Ard Biesheuvel >> <ard.biesheuvel@linaro.org> wrote: >>> Hi Kees, >>> >>> On 22 June 2017 at 18:06, Kees Cook <keescook@chromium.org> wrote: >>>> Now that explicitly executed loaders are loaded in the mmap region, >>>> position PIE binaries lower in the address space to avoid possible >>>> collisions with mmap or stack regions. For 64-bit, align to 4GB to >>>> allow runtimes to use the entire 32-bit address space for 32-bit >>>> pointers. >>>> >>>> Signed-off-by: Kees Cook <keescook@chromium.org> >>>> --- >>>> arch/arm64/include/asm/elf.h | 13 ++++++------- >>>> 1 file changed, 6 insertions(+), 7 deletions(-) >>>> >>>> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h >>>> index 5d1700425efe..f742af8f7c42 100644 >>>> --- a/arch/arm64/include/asm/elf.h >>>> +++ b/arch/arm64/include/asm/elf.h >>>> @@ -113,12 +113,13 @@ >>>> #define ELF_EXEC_PAGESIZE PAGE_SIZE >>>> >>>> /* >>>> - * This is the location that an ET_DYN program is loaded if exec'ed. Typical >>>> - * use of this is to invoke "./ld.so someprog" to test out a new version of >>>> - * the loader. We need to make sure that it is out of the way of the program >>>> - * that it will "exec", and that there is sufficient room for the brk. >>>> + * This is the base location for PIE (ET_DYN with INTERP) loads. On >>>> + * 64-bit, this is raised to 4GB to leave the entire 32-bit address >>>> + * space open for things that want to use the area for 32-bit pointers. >>>> */ >>>> -#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3) >>>> +#define ELF_ET_DYN_BASE (test_thread_flag(TIF_32BIT) ? \ >>>> + 0x000400000UL : \ >>>> + 0x100000000UL) >>>> >>> >>> Why are you merging this with the COMPAT definition? >> >> It seemed like the right thing to do since a single definition could >> handle both cases. Is there something I'm overlooking in the arm64 >> case? > > And like 5 minutes later there was a loud head-slapping noise in my > office. Durr, yeah, arm64 doesn't have to deal with a "native 32-bit" > mode, so the merge isn't needed. Yes yes, I will split it back up and > drop the thread flag test. > Oh, is that what I heard?
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 5d1700425efe..f742af8f7c42 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -113,12 +113,13 @@ #define ELF_EXEC_PAGESIZE PAGE_SIZE /* - * This is the location that an ET_DYN program is loaded if exec'ed. Typical - * use of this is to invoke "./ld.so someprog" to test out a new version of - * the loader. We need to make sure that it is out of the way of the program - * that it will "exec", and that there is sufficient room for the brk. + * This is the base location for PIE (ET_DYN with INTERP) loads. On + * 64-bit, this is raised to 4GB to leave the entire 32-bit address + * space open for things that want to use the area for 32-bit pointers. */ -#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3) +#define ELF_ET_DYN_BASE (test_thread_flag(TIF_32BIT) ? \ + 0x000400000UL : \ + 0x100000000UL) #ifndef __ASSEMBLY__ @@ -173,8 +174,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm, #ifdef CONFIG_COMPAT -#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3) - /* AArch32 registers. */ #define COMPAT_ELF_NGREG 18 typedef unsigned int compat_elf_greg_t;
Now that explicitly executed loaders are loaded in the mmap region, position PIE binaries lower in the address space to avoid possible collisions with mmap or stack regions. For 64-bit, align to 4GB to allow runtimes to use the entire 32-bit address space for 32-bit pointers. Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/arm64/include/asm/elf.h | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)