From: Catalin Marinas <catalin.marinas@arm.com>
To: Dev Jain <dev.jain@arm.com>
Cc: akpm@linux-foundation.org, david@kernel.org, urezki@gmail.com,
kees@kernel.org, mingo@redhat.com, peterz@infradead.org,
juri.lelli@redhat.com, vincent.guittot@linaro.org, arnd@arndb.de,
Muhammad Usama Anjum <usama.anjum@arm.com>,
ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org,
rppt@kernel.org, surenb@google.com, mhocko@suse.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, vschneid@redhat.com,
kprateek.nayak@amd.com, tglx@kernel.org,
mathieu.desnoyers@efficios.com, linux-arch@vger.kernel.org,
ryan.roberts@arm.com
Subject: Re: [PATCH v4 2/3] kasan: skip HW tagging for all kernel thread stacks
Date: Wed, 29 Apr 2026 15:43:23 +0100 [thread overview]
Message-ID: <afIY9zevao9S3zKy@arm.com> (raw)
In-Reply-To: <20260429102704.680174-3-dev.jain@arm.com>
On Wed, Apr 29, 2026 at 03:57:03PM +0530, Dev Jain wrote:
> From: Muhammad Usama Anjum <usama.anjum@arm.com>
>
> HW-tag KASAN never checks kernel stacks because stack pointers carry the
> match-all tag, so setting/poisoning tags is pure overhead.
>
> - Add __GFP_SKIP_KASAN to THREADINFO_GFP so every stack allocator that
> uses it skips tagging (fork path plus arch users)
> - Add __GFP_SKIP_KASAN to GFP_VMAP_STACK for the fork-specific vmap
> stacks.
> - When reusing cached vmap stacks, skip kasan_unpoison_range() if HW tags
> are enabled.
>
> Software KASAN is unchanged; this only affects tag-based KASAN.
>
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
next prev parent reply other threads:[~2026-04-29 14:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-29 10:27 [PATCH v4 0/3] kasan: hw_tags: Disable tagging for stack and page-tables Dev Jain
2026-04-29 10:27 ` [PATCH v4 1/3] vmalloc: add __GFP_SKIP_KASAN support Dev Jain
2026-04-29 14:42 ` Catalin Marinas
2026-04-29 10:27 ` [PATCH v4 2/3] kasan: skip HW tagging for all kernel thread stacks Dev Jain
2026-04-29 14:43 ` Catalin Marinas [this message]
2026-04-29 10:27 ` [PATCH v4 3/3] mm: skip KASAN tagging for page-allocated page tables Dev Jain
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