| Message ID | 1594613013-13059-1-git-send-email-guoren@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Make TSK_STACK_CANARY more accurate defined | expand |
On Mon, Jul 13, 2020 at 04:03:33AM +0000, guoren@kernel.org wrote: > From: Guo Ren <guoren@linux.alibaba.com> > > TSK_STACK_CANARY only used in arm64/Makefile with > CONFIG_STACKPROTECTOR_PER_TASK wrap. So use the same policy in > asm-offset.c. > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > Co-developed-by: Kees Cook <keescook@chromium.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > --- > arch/arm64/kernel/asm-offsets.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c > index 0577e21..37d5d3d 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -39,7 +39,7 @@ int main(void) > DEFINE(TSK_TI_SCS_SP, offsetof(struct task_struct, thread_info.scs_sp)); > #endif > DEFINE(TSK_STACK, offsetof(struct task_struct, stack)); > -#ifdef CONFIG_STACKPROTECTOR > +#ifdef CONFIG_STACKPROTECTOR_PER_TASK > DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary)); > #endif I don't think this really makese much sense. The 'stack_canary' field in 'struct task_struct' is defined as: #ifdef CONFIG_STACKPROTECTOR /* Canary value for the -fstack-protector GCC feature: */ unsigned long stack_canary; #endif so I think it makes sense to follow that in asm-offsets.c Does the current code actually cause a problem? Will
On 2020/7/14 下午4:37, Will Deacon wrote: > On Mon, Jul 13, 2020 at 04:03:33AM +0000, guoren@kernel.org wrote: >> From: Guo Ren <guoren@linux.alibaba.com> >> >> TSK_STACK_CANARY only used in arm64/Makefile with >> CONFIG_STACKPROTECTOR_PER_TASK wrap. So use the same policy in >> asm-offset.c. >> >> Signed-off-by: Guo Ren <guoren@linux.alibaba.com> >> Co-developed-by: Kees Cook <keescook@chromium.org> >> Cc: Catalin Marinas <catalin.marinas@arm.com> >> Cc: Will Deacon <will@kernel.org> >> --- >> arch/arm64/kernel/asm-offsets.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c >> index 0577e21..37d5d3d 100644 >> --- a/arch/arm64/kernel/asm-offsets.c >> +++ b/arch/arm64/kernel/asm-offsets.c >> @@ -39,7 +39,7 @@ int main(void) >> DEFINE(TSK_TI_SCS_SP, offsetof(struct task_struct, thread_info.scs_sp)); >> #endif >> DEFINE(TSK_STACK, offsetof(struct task_struct, stack)); >> -#ifdef CONFIG_STACKPROTECTOR >> +#ifdef CONFIG_STACKPROTECTOR_PER_TASK >> DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary)); >> #endif > I don't think this really makese much sense. The 'stack_canary' field in > 'struct task_struct' is defined as: > > #ifdef CONFIG_STACKPROTECTOR > /* Canary value for the -fstack-protector GCC feature: */ > unsigned long stack_canary; > #endif > > so I think it makes sense to follow that in asm-offsets.c > > Does the current code actually cause a problem? No, I just want to know how arm64 reply, ref: https://lore.kernel.org/linux-riscv/1594397998-10221-1-git-send-email-guoren@kernel.org/T/#t Best Regards Guo Ren
BTW, Jim found a GCC security leak in arm64, and would you want to
have a look at it?
-------
I notice in the epilogue I get
ld a4, 8(sp)
ld a5, 100(t6)
xor a5, a4, a5
bne a5,zero,.L4
This looks like a security leak that the canary value is left in a4.
The i386 implementation operates directly on memory without loading
into registers. The rs6000 implementation is careful to load 0 into
the other register in the stack_protector_test code after the xor. I
think this is a bug in the aarch64 code that it isn't clearing the
other register. And I think it is a bug in your code too. If we
don't need to clear the canary from the two registers, then you should
eliminate the xor and just use "bne a5,a4,.L4". But I think the way
you have it is right, you just need to clear the a4 register after the
xor.
--------
[1] https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549910.html
On Tue, Jul 14, 2020 at 4:37 PM Will Deacon <will@kernel.org> wrote:
>
> On Mon, Jul 13, 2020 at 04:03:33AM +0000, guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > TSK_STACK_CANARY only used in arm64/Makefile with
> > CONFIG_STACKPROTECTOR_PER_TASK wrap. So use the same policy in
> > asm-offset.c.
> >
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Co-developed-by: Kees Cook <keescook@chromium.org>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> > ---
> > arch/arm64/kernel/asm-offsets.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> > index 0577e21..37d5d3d 100644
> > --- a/arch/arm64/kernel/asm-offsets.c
> > +++ b/arch/arm64/kernel/asm-offsets.c
> > @@ -39,7 +39,7 @@ int main(void)
> > DEFINE(TSK_TI_SCS_SP, offsetof(struct task_struct, thread_info.scs_sp));
> > #endif
> > DEFINE(TSK_STACK, offsetof(struct task_struct, stack));
> > -#ifdef CONFIG_STACKPROTECTOR
> > +#ifdef CONFIG_STACKPROTECTOR_PER_TASK
> > DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary));
> > #endif
>
> I don't think this really makese much sense. The 'stack_canary' field in
> 'struct task_struct' is defined as:
>
> #ifdef CONFIG_STACKPROTECTOR
> /* Canary value for the -fstack-protector GCC feature: */
> unsigned long stack_canary;
> #endif
>
> so I think it makes sense to follow that in asm-offsets.c
>
> Does the current code actually cause a problem?
>
> Will
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
On Fri, Jul 17, 2020 at 08:56:23AM +0800, Guo Ren wrote: > BTW, Jim found a GCC security leak in arm64, and would you want to > have a look at it? Thanks. This seems to be tracked in their bugzilla here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96191 I agree with Jim that this should be fixed. Will
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 0577e21..37d5d3d 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -39,7 +39,7 @@ int main(void) DEFINE(TSK_TI_SCS_SP, offsetof(struct task_struct, thread_info.scs_sp)); #endif DEFINE(TSK_STACK, offsetof(struct task_struct, stack)); -#ifdef CONFIG_STACKPROTECTOR +#ifdef CONFIG_STACKPROTECTOR_PER_TASK DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary)); #endif BLANK();