Messages in this thread |  | | From | Kees Cook <> | Date | Fri, 30 Jun 2017 11:27:03 -0700 | Subject | Re: [PATCH v2] ARM: fix randomized task_struct |
| |
On Fri, Jun 30, 2017 at 9:03 AM, Arnd Bergmann <arnd@arndb.de> wrote: > With the new task struct randomization, we can run into a build > failure for certain random seeds: > > arch/arm/kernel/entry-armv.S: Assembler messages: > arch/arm/kernel/entry-armv.S:803: Error: bad immediate value for offset (4096) > > Only two constants in asm-offset.h are affected, and I'm changing > both of them here to work correctly in all configurations. > > One more macro has the problem, but is currently unused, so this > removes it instead of adding complexity. > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Fixes: c33d8b12fbbd ("task_struct: Allow randomized layout") > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Looks great, thanks!
Reviewed-by: Kees Cook <keescook@chromium.org>
Russell, if you're happy with it can you Ack this? I'd like to carry the change in the randstruct tree (so all the dependencies are in the same tree).
-Kees
> --- > v2: define a more appropriate macro instead of PAGE_MASK, > fix always-true comparison to test the right thing > --- > arch/arm/include/asm/assembler.h | 2 ++ > arch/arm/kernel/entry-armv.S | 5 ++++- > arch/arm/mm/proc-macros.S | 10 ++++------ > 3 files changed, 10 insertions(+), 7 deletions(-) > > diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h > index 68b06f9c65de..ad301f107dd2 100644 > --- a/arch/arm/include/asm/assembler.h > +++ b/arch/arm/include/asm/assembler.h > @@ -87,6 +87,8 @@ > #define CALGN(code...) > #endif > > +#define IMM12_MASK 0xfff > + > /* > * Enable and disable interrupts > */ > diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S > index 9f157e7c51e7..c731f0d2b2af 100644 > --- a/arch/arm/kernel/entry-armv.S > +++ b/arch/arm/kernel/entry-armv.S > @@ -797,7 +797,10 @@ ENTRY(__switch_to) > #if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) > ldr r7, [r2, #TI_TASK] > ldr r8, =__stack_chk_guard > - ldr r7, [r7, #TSK_STACK_CANARY] > + .if (TSK_STACK_CANARY > IMM12_MASK) > + add r7, r7, #TSK_STACK_CANARY & ~IMM12_MASK > + .endif > + ldr r7, [r7, #TSK_STACK_CANARY & IMM12_MASK] > #endif > #ifdef CONFIG_CPU_USE_DOMAINS > mcr p15, 0, r6, c3, c0, 0 @ Set domain register > diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S > index 0d40c285bd86..f944836da8a2 100644 > --- a/arch/arm/mm/proc-macros.S > +++ b/arch/arm/mm/proc-macros.S > @@ -25,11 +25,6 @@ > ldr \rd, [\rn, #VMA_VM_FLAGS] > .endm > > - .macro tsk_mm, rd, rn > - ldr \rd, [\rn, #TI_TASK] > - ldr \rd, [\rd, #TSK_ACTIVE_MM] > - .endm > - > /* > * act_mm - get current->active_mm > */ > @@ -37,7 +32,10 @@ > bic \rd, sp, #8128 > bic \rd, \rd, #63 > ldr \rd, [\rd, #TI_TASK] > - ldr \rd, [\rd, #TSK_ACTIVE_MM] > + .if (TSK_ACTIVE_MM > IMM12_MASK) > + add \rd, \rd, #TSK_ACTIVE_MM & ~IMM12_MASK > + .endif > + ldr \rd, [\rd, #TSK_ACTIVE_MM & IMM12_MASK] > .endm > > /* > -- > 2.9.0 >
-- Kees Cook Pixel Security
|  |