From 1dddd25125112ba49706518ac9077a1026a18f37 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 4 Jan 2018 12:32:03 +0100
Subject: x86/kaslr: Fix the vaddr_end mess
vaddr_end for KASLR is only documented in the KASLR code itself and is
adjusted depending on config options. So it's not surprising that a change
of the memory layout causes KASLR to have the wrong vaddr_end. This can map
arbitrary stuff into other areas causing hard to understand problems.
Remove the whole ifdef magic and define the start of the cpu_entry_area to
be the end of the KASLR vaddr range.
Add documentation to that effect.
Fixes: 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap")
Reported-by: Benjamin Gilbert <benjamin.gilbert@coreos.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Benjamin Gilbert <benjamin.gilbert@coreos.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable <stable@vger.kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Garnier <thgarnie@google.com>,
Cc: Alexander Kuleshov <kuleshovmail@gmail.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801041320360.1771@nanos
---
arch/x86/mm/kaslr.c | 32 +++++++++-----------------------
1 file changed, 9 insertions(+), 23 deletions(-)
(limited to 'arch/x86/mm/kaslr.c')
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index 879ef930e2c2..aedebd2ebf1e 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -34,25 +34,14 @@
#define TB_SHIFT 40
/*
- * Virtual address start and end range for randomization. The end changes base
- * on configuration to have the highest amount of space for randomization.
- * It increases the possible random position for each randomized region.
+ * Virtual address start and end range for randomization.
*
- * You need to add an if/def entry if you introduce a new memory region
- * compatible with KASLR. Your entry must be in logical order with memory
- * layout. For example, ESPFIX is before EFI because its virtual address is
- * before. You also need to add a BUILD_BUG_ON() in kernel_randomize_memory() to
- * ensure that this order is correct and won't be changed.
+ * The end address could depend on more configuration options to make the
+ * highest amount of space for randomization available, but that's too hard
+ * to keep straight and caused issues already.
*/
static const unsigned long vaddr_start = __PAGE_OFFSET_BASE;
-
-#if defined(CONFIG_X86_ESPFIX64)
-static const unsigned long vaddr_end = ESPFIX_BASE_ADDR;
-#elif defined(CONFIG_EFI)
-static const unsigned long vaddr_end = EFI_VA_END;
-#else
-static const unsigned long vaddr_end = __START_KERNEL_map;
-#endif
+static const unsigned long vaddr_end = CPU_ENTRY_AREA_BASE;
/* Default values */
unsigned long page_offset_base = __PAGE_OFFSET_BASE;
@@ -101,15 +90,12 @@ void __init kernel_randomize_memory(void)
unsigned long remain_entropy;
/*
- * All these BUILD_BUG_ON checks ensures the memory layout is
- * consistent with the vaddr_start/vaddr_end variables.
+ * These BUILD_BUG_ON checks ensure the memory layout is consistent
+ * with the vaddr_start/vaddr_end variables. These checks are very
+ * limited....
*/
BUILD_BUG_ON(vaddr_start >= vaddr_end);
- BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) &&
- vaddr_end >= EFI_VA_END);
- BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) ||
- IS_ENABLED(CONFIG_EFI)) &&
- vaddr_end >= __START_KERNEL_map);
+ BUILD_BUG_ON(vaddr_end != CPU_ENTRY_AREA_BASE);
BUILD_BUG_ON(vaddr_end > __START_KERNEL_map);
if (!kaslr_memory_enabled())
--
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