linux-kernel - [PATCH] arm64: Fix KASAN random tag seed initialization

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Message-ID: <20240814091005.969756-1-samuel.holland@sifive.com>
Date: Wed, 14 Aug 2024 02:09:53 -0700
From: Samuel Holland <samuel.holland@...ive.com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Samuel Holland <samuel.holland@...ive.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Douglas Anderson <dianders@...omium.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	James Morse <james.morse@....com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Mark Rutland <mark.rutland@....com>,
	Puranjay Mohan <puranjay@...nel.org>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Ryo Takakura <takakura@...inux.co.jp>,
	Shaoqin Huang <shahuang@...hat.com>,
	Stephen Boyd <swboyd@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <will@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] arm64: Fix KASAN random tag seed initialization

Currently, kasan_init_sw_tags() is called before setup_per_cpu_areas(),
so per_cpu(prng_state, cpu) accesses the same address regardless of the
value of "cpu", and the same seed value gets copied to the percpu area
for every CPU. Fix this by moving the call to smp_prepare_boot_cpu(),
which is the first architecture hook after setup_per_cpu_areas().

Fixes: 3c9e3aa11094 ("kasan: add tag related helper functions")
Fixes: 3f41b6093823 ("kasan: fix random seed generation for tag-based mode")
Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
---

 arch/arm64/kernel/setup.c | 3 ---
 arch/arm64/kernel/smp.c   | 2 ++
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index a096e2451044..b22d28ec8028 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -355,9 +355,6 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
 	smp_init_cpus();
 	smp_build_mpidr_hash();
 
-	/* Init percpu seeds for random tags after cpus are set up. */
-	kasan_init_sw_tags();
-
 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 	/*
 	 * Make sure init_thread_info.ttbr0 always generates translation
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 5e18fbcee9a2..f01f0fd7b7fe 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -467,6 +467,8 @@ void __init smp_prepare_boot_cpu(void)
 		init_gic_priority_masking();
 
 	kasan_init_hw_tags();
+	/* Init percpu seeds for random tags after cpus are set up. */
+	kasan_init_sw_tags();
 }
 
 /*
-- 
2.45.1