52 lines
1.9 KiB
Diff
52 lines
1.9 KiB
Diff
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From 47fb1f1e6e64d2d6f1c313c5096f6b0a0da19011 Mon Sep 17 00:00:00 2001
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Thu, 16 Dec 2010 14:25:18 +0100
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Subject: [PATCH 205/365] x86: stackprotector: Avoid random pool on rt
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CPU bringup calls into the random pool to initialize the stack
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canary. During boot that works nicely even on RT as the might sleep
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checks are disabled. During CPU hotplug the might sleep checks
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trigger. Making the locks in random raw is a major PITA, so avoid the
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call on RT is the only sensible solution. This is basically the same
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randomness which we get during boot where the random pool has no
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entropy and we rely on the TSC randomnness.
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Reported-by: Carsten Emde <carsten.emde@osadl.org>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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arch/x86/include/asm/stackprotector.h | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
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index 743bd2d77e51..e1fabfcddd65 100644
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--- a/arch/x86/include/asm/stackprotector.h
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+++ b/arch/x86/include/asm/stackprotector.h
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@@ -64,7 +64,7 @@
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*/
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static __always_inline void boot_init_stack_canary(void)
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{
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- u64 canary;
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+ u64 uninitialized_var(canary);
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u64 tsc;
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#ifdef CONFIG_X86_64
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@@ -75,8 +75,15 @@ static __always_inline void boot_init_stack_canary(void)
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* of randomness. The TSC only matters for very early init,
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* there it already has some randomness on most systems. Later
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* on during the bootup the random pool has true entropy too.
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+ *
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+ * For preempt-rt we need to weaken the randomness a bit, as
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+ * we can't call into the random generator from atomic context
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+ * due to locking constraints. We just leave canary
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+ * uninitialized and use the TSC based randomness on top of it.
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*/
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+#ifndef CONFIG_PREEMPT_RT_FULL
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get_random_bytes(&canary, sizeof(canary));
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+#endif
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tsc = rdtsc();
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canary += tsc + (tsc << 32UL);
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--
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2.28.0
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