Messages in this thread | | | Date | Wed, 15 Sep 2021 10:19:43 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] [RFC]arm64:Mark __stack_chk_guard as __ro_after_init |
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On Wed, Sep 15, 2021 at 09:57:14AM +0800, ashimida wrote: > Hi King, Rutland: > > Thanks for the reply and let me understand the reason here. > > Then may I first submit a patch to modify the attributes of > __stack_chk_guard of the arm/aarch64 platform?
This patch looks fine as-is (hence the Acked-by). Doing the same for arch/arm makes sense, but that should be a separate patch.
I was suggesting that in future we should probably do the same in more places, not that you need to do so now.
Thanks, Mark.
> > On 9/14/21 6:17 PM, Mark Rutland wrote: > > On Tue, Sep 14, 2021 at 05:44:02PM +0800, Dan Li wrote: > > > __stack_chk_guard is setup once while init stage and never changed > > > after that. > > > > > > Although the modification of this variable at runtime will usually > > > cause the kernel to crash (so dose the attacker), it should be marked > > > as _ro_after_init, and it should not affect performance if it is > > > placed in the ro_after_init section. > > > > > > This should also be the case on the ARM platform, or am I missing > > > something? > > > > > > Signed-off-by: Dan Li <ashimida@linux.alibaba.com> > > > > FWIW, this makes sense to me: > > > > Acked-by: Mark Rutland <mark.rutland@arm.com> > > > > Looking at the history, this was added to arm64 in commit: > > > > c0c264ae5112d1cd ("arm64: Add CONFIG_CC_STACKPROTECTOR") > > > > ... whereas __ro_after_init was introduced around 2 years later in > > commit: > > > > c74ba8b3480da6dd ("arch: Introduce post-init read-only memory") > > > > ... so we weren't deliberately avoiding __ro_after_init, and there are > > probably a significant number of other variables we could apply it to. > > > > Mark. > > > > > --- > > > arch/arm64/kernel/process.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > > > index c8989b9..c858b85 100644 > > > --- a/arch/arm64/kernel/process.c > > > +++ b/arch/arm64/kernel/process.c > > > @@ -60,7 +60,7 @@ > > > #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK) > > > #include <linux/stackprotector.h> > > > -unsigned long __stack_chk_guard __read_mostly; > > > +unsigned long __stack_chk_guard __ro_after_init; > > > EXPORT_SYMBOL(__stack_chk_guard); > > > #endif > > > -- > > > 2.7.4 > > >
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