diff mbox

[v2,01/11] crypto: xcbc: Remove VLA usage

Message ID 4d9f90abbf87539d3588f88117806f76c6826030.camel@perches.com (mailing list archive)
State Superseded, archived
Delegated to: Mike Snitzer
Headers show

Commit Message

Joe Perches June 25, 2018, 9:23 p.m. UTC
On Mon, 2018-06-25 at 14:10 -0700, Kees Cook wrote:
> In the quest to remove all stack VLA usage from the kernel[1], this uses
> the maximum blocksize and adds a sanity check. For xcbc, the blocksize
> must always be 16, so use that, since it's already being enforced during
> instantiation.

Is it time yet to change this warning from 'make W=3' to W=1?
---
 scripts/Makefile.extrawarn | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

 warning += $(warning-$(findstring 2,
$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))

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Comments

Kees Cook June 25, 2018, 9:32 p.m. UTC | #1
On Mon, Jun 25, 2018 at 2:23 PM, Joe Perches <joe@perches.com> wrote:
> On Mon, 2018-06-25 at 14:10 -0700, Kees Cook wrote:
>> In the quest to remove all stack VLA usage from the kernel[1], this uses
>> the maximum blocksize and adds a sanity check. For xcbc, the blocksize
>> must always be 16, so use that, since it's already being enforced during
>> instantiation.
>
> Is it time yet to change this warning from 'make W=3' to W=1?
> ---
>  scripts/Makefile.extrawarn | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 8d5357053f86..27ba478d40cd 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -29,6 +29,7 @@ warning-1 += $(call cc-option, -Wmissing-include-dirs)
>  warning-1 += $(call cc-option, -Wunused-but-set-variable)
>  warning-1 += $(call cc-option, -Wunused-const-variable)
>  warning-1 += $(call cc-option, -Wpacked-not-aligned)
> +warning-1 += $(call cc-option, -Wvla)
>  warning-1 += $(call cc-disable-warning, missing-field-initializers)
>  warning-1 += $(call cc-disable-warning, sign-compare)
>
> @@ -52,7 +53,6 @@ warning-3 += -Wpointer-arith
>  warning-3 += -Wredundant-decls
>  warning-3 += -Wswitch-default
>  warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
> -warning-3 += $(call cc-option, -Wvla)
>
>  warning := $(warning-$(findstring 1,
> $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
>  warning += $(warning-$(findstring 2,
> $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))

I was going to skip the churn since I intend to make the default build
use -Wvla for the next merge window (assuming we've killed all the
VLAs by then). After crypto, only fs/ntfs remains, and I have that
half done already. There are a couple more still under some
development back-and-forth.

I'm not _opposed_ to this change, but I'd rather just make it the
default. And then the next cycle, I'd want it to be -Werror=vla, but I
may get shouted down. ;)

-Kees
Joe Perches June 25, 2018, 9:38 p.m. UTC | #2
On Mon, 2018-06-25 at 14:32 -0700, Kees Cook wrote:
> On Mon, Jun 25, 2018 at 2:23 PM, Joe Perches <joe@perches.com> wrote:
> > On Mon, 2018-06-25 at 14:10 -0700, Kees Cook wrote:
> > > In the quest to remove all stack VLA usage from the kernel[1], this uses
> > > the maximum blocksize and adds a sanity check. For xcbc, the blocksize
> > > must always be 16, so use that, since it's already being enforced during
> > > instantiation.
> > 
> > Is it time yet to change this warning from 'make W=3' to W=1?
[]
> I was going to skip the churn since I intend to make the default build
> use -Wvla for the next merge window (assuming we've killed all the
> VLAs by then).

Good.

Even if not all VLAs are removed, making the
warning default on is fine by me.

Getting others to do some of the work you've
been doing would be good too.

> After crypto, only fs/ntfs remains, and I have that
> half done already. There are a couple more still under some
> development back-and-forth.
> 
> I'm not _opposed_ to this change, but I'd rather just make it the
> default. And then the next cycle, I'd want it to be -Werror=vla, but I
> may get shouted down. ;)

Yup, you should get shouted down there.
I think -Werror=<anything> is poor form.

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diff mbox

Patch

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 8d5357053f86..27ba478d40cd 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -29,6 +29,7 @@  warning-1 += $(call cc-option, -Wmissing-include-dirs)
 warning-1 += $(call cc-option, -Wunused-but-set-variable)
 warning-1 += $(call cc-option, -Wunused-const-variable)
 warning-1 += $(call cc-option, -Wpacked-not-aligned)
+warning-1 += $(call cc-option, -Wvla)
 warning-1 += $(call cc-disable-warning, missing-field-initializers)
 warning-1 += $(call cc-disable-warning, sign-compare)
 
@@ -52,7 +53,6 @@  warning-3 += -Wpointer-arith
 warning-3 += -Wredundant-decls
 warning-3 += -Wswitch-default
 warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
-warning-3 += $(call cc-option, -Wvla)
 
 warning := $(warning-$(findstring 1,
$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))