On Tue, 22 Jun 2021 at 12:48, Yee Lee <yee.lee@xxxxxxxxxxxx> wrote: > > On Tue, 2021-06-22 at 11:01 +0200, Marco Elver wrote: > > On Tue, 22 Jun 2021 at 10:48, <yee.lee@xxxxxxxxxxxx> wrote: > > > > > > From: Yee Lee <yee.lee@xxxxxxxxxxxx> > > > > > > Follows the discussion: > > > https://patchwork.kernel.org/project/linux-mediatek/list/?series=504439 > > > > The info about the percentage of how frequent this is could have been > > provided as a simple reply to the discussion. > > > > > This patch Add memzero_explict to initialize unaligned object. > > > > This patch does not apply to anything (I see it depends on the > > previous patch). > > > > What you need to do is modify the original patch, and then send a > > [PATCH v2] (git helps with that by passing --reroll-count or -v) that > > applies cleanly to your base kernel tree. > > > > The commit message will usually end with '---' and then briefly > > denote > > what changed since the last version. > > > Got it. > > > > https://www.kernel.org/doc/html/latest/process/submitting-patches.html#the-canonical-patch-format > > > > > Based on the integrateion of initialization in kasan_unpoison(). > > > The hwtag instructions, constrained with its granularity, has to > > > overwrite the data btyes in unaligned objects. This would cause > > > issue when it works with SLUB debug redzoning. > > > > > > In this patch, an additional initalizaing path is added for the > > > unaligned objects. It contains memzero_explict() to clear out the > > > data and disables its init flag for the following hwtag actions. > > > > > > In lab test, this path is executed about 1.1%(941/80854) within the > > > overall kasan_unpoison during a non-debug booting process. > > > > Nice, thanks for the data. If it is somehow doable, however, I'd > > still > > recommend to additionally guard the new code path by a check if > > debug-support was requested. Ideally with an IS_ENABLED() config > > check > > so that if it's a production kernel the branch is simply optimized > > out > > by the compiler. > > Does it mean the memzero code path would be applied only at > CONFIG_DEBUG_SLUB enabled? It expects no other potential overwriting > in non-debug kernel. Yes, if the problem only occurs with slub debugging enabled. > By the way, based on de-coupling principle, adding a specific > conditional statement(is_enable slub_debug) in a primitive > funciton(kasan_unpoison) is not neat. It may be more proper that the > conditional statement be added in other procedures of slub alloc. What do you have in mind? Well, there is kmem_cache_debug_flags(). Perhaps there's a better place to add the check? > Thanks, > > BR, > Yee > > > > > > Lab test: QEMU5.2 (+mte) / linux kernel 5.13-rc7 > > > > > > Signed-off-by: Yee Lee <yee.lee@xxxxxxxxxxxx> > > > --- > > > mm/kasan/kasan.h | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > > > index d8faa64614b7..edc11bcc3ff3 100644 > > > --- a/mm/kasan/kasan.h > > > +++ b/mm/kasan/kasan.h > > > @@ -389,7 +389,7 @@ static inline void kasan_unpoison(const void > > > *addr, size_t size, bool init) > > > return; > > > if (init && ((unsigned long)size & KASAN_GRANULE_MASK)) { > > > init = false; > > > - memset((void *)addr, 0, size); > > > + memzero_explicit((void *)addr, size); > > > } > > > size = round_up(size, KASAN_GRANULE_SIZE); > > > hw_set_mem_tag_range((void *)addr, size, tag, init); > > > 2.18.0 > > > > > > -- > > > You received this message because you are subscribed to the Google > > > Groups "kasan-dev" group. > > > To unsubscribe from this group and stop receiving emails from it, > > > send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > > > To view this discussion on the web visit > > > https://groups.google.com/d/msgid/kasan-dev/20210622084723.27637-1-yee.lee%40mediatek.com > > > . > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/46b1468146206e6cef0c33ecbfd86e02ea819db4.camel%40mediatek.com.
