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authorAndrey Konovalov <andreyknvl@google.com>2019-02-20 22:20:15 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-02-21 09:01:00 -0800
commit3f41b609382388f95c0a05b69b8db0d706adafb4 (patch)
treecf5fed9746400cbda15f47acd7acceab80aa1fd5 /arch/arm64
parenttmpfs: fix link accounting when a tmpfile is linked in (diff)
downloadlinux-dev-3f41b609382388f95c0a05b69b8db0d706adafb4.tar.xz
linux-dev-3f41b609382388f95c0a05b69b8db0d706adafb4.zip
kasan: fix random seed generation for tag-based mode
There are two issues with assigning random percpu seeds right now: 1. We use for_each_possible_cpu() to iterate over cpus, but cpumask is not set up yet at the moment of kasan_init(), and thus we only set the seed for cpu #0. 2. A call to get_random_u32() always returns the same number and produces a message in dmesg, since the random subsystem is not yet initialized. Fix 1 by calling kasan_init_tags() after cpumask is set up. Fix 2 by using get_cycles() instead of get_random_u32(). This gives us lower quality random numbers, but it's good enough, as KASAN is meant to be used as a debugging tool and not a mitigation. Link: http://lkml.kernel.org/r/1f815cc914b61f3516ed4cc9bfd9eeca9bd5d9de.1550677973.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kernel/setup.c3
-rw-r--r--arch/arm64/mm/kasan_init.c2
2 files changed, 3 insertions, 2 deletions
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index d09ec76f08cf..009849328289 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -339,6 +339,9 @@ void __init 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_tags();
+
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
/*
* Make sure init_thread_info.ttbr0 always generates translation
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 4b55b15707a3..f37a86d2a69d 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -252,8 +252,6 @@ void __init kasan_init(void)
memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
- kasan_init_tags();
-
/* At this point kasan is fully initialized. Enable error messages */
init_task.kasan_depth = 0;
pr_info("KernelAddressSanitizer initialized\n");