From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1C5553D5223; Wed, 29 Apr 2026 10:28:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777458493; cv=none; b=KOO2dWRZ0DK2cpWo+4e0SMMVUtYZfckp8CpeRRPm7FuL7MgBYtUPWE813VvNt53q6kTIiJ7NnuAS59F2hScKpXQjtHCVf+SqDr0B2sCUoNxVQIaqF6/6PHzP+IDkGMlMHDBryqNRe51JIz5+R9ONoe4lLlkYtDea73IHDc211A4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777458493; c=relaxed/simple; bh=orXsq89dfQMCSKEE6gPmHluNEOO7CXeI2G3nz7AJ8FI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Hg71AJUBrwqw6CiKifKB9IyeuIYFpFzKz1G1RRlhcIiwS2MOKXAAKpYmnZaPpwXmTTAm6BooObUr20Jv1OKN5Ep8l1/ijy9bh2AKWzcoandKoi6w0tt9vqjoLDvmr3dSpqRwMK53zZ68LtD9iEOWvlRWYTJJ3SOGTQqtZFLC0pU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=ESGGwOF8; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="ESGGwOF8" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F315C2A68; Wed, 29 Apr 2026 03:28:05 -0700 (PDT) Received: from a080796.blr.arm.com (a080796.arm.com [10.164.21.51]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 27B373F763; Wed, 29 Apr 2026 03:28:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777458491; bh=orXsq89dfQMCSKEE6gPmHluNEOO7CXeI2G3nz7AJ8FI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ESGGwOF8xqj5DfideHRgMZPn34oyBQ6v/NvyCJ/O6ZI8vg7vKVveDC/MpnPb6fhwj aw3fI5JsSJb1H0svna9O1P6MJOvk+cOzwAzkiPO5rCLHD8VxJuCWDKgok+U8ys1LOi YzxVjTJulqfYNz6cPeW/GcShU6dm60uDJwDqghz4= From: Dev Jain To: 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 Cc: Muhammad Usama Anjum , 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, catalin.marinas@arm.com, Dev Jain Subject: [PATCH v4 2/3] kasan: skip HW tagging for all kernel thread stacks Date: Wed, 29 Apr 2026 15:57:03 +0530 Message-Id: <20260429102704.680174-3-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260429102704.680174-1-dev.jain@arm.com> References: <20260429102704.680174-1-dev.jain@arm.com> Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Muhammad Usama Anjum 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 Signed-off-by: Dev Jain --- include/linux/thread_info.h | 2 +- kernel/fork.c | 5 +++-- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h index 051e429026904..307b8390fc670 100644 --- a/include/linux/thread_info.h +++ b/include/linux/thread_info.h @@ -92,7 +92,7 @@ static inline long set_restart_fn(struct restart_block *restart, #define THREAD_ALIGN THREAD_SIZE #endif -#define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO) +#define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_SKIP_KASAN) /* * flag set/clear/test wrappers diff --git a/kernel/fork.c b/kernel/fork.c index f1ad69c6dc2d4..0d97fd71d7f60 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -204,7 +204,7 @@ static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); * accounting is performed by the code assigning/releasing stacks to tasks. * We need a zeroed memory without __GFP_ACCOUNT. */ -#define GFP_VMAP_STACK (GFP_KERNEL | __GFP_ZERO) +#define GFP_VMAP_STACK (GFP_KERNEL | __GFP_ZERO | __GFP_SKIP_KASAN) struct vm_stack { struct rcu_head rcu; @@ -342,7 +342,8 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) } /* Reset stack metadata. */ - kasan_unpoison_range(vm_area->addr, THREAD_SIZE); + if (!kasan_hw_tags_enabled()) + kasan_unpoison_range(vm_area->addr, THREAD_SIZE); stack = kasan_reset_tag(vm_area->addr); -- 2.34.1