xtensa/mm: Stop printing the virtual memory layout

Commit Message

Arvind Sankar March 5, 2020, 3:11 p.m. UTC

For security, don't display the kernel's virtual memory layout.

Kees Cook points out:
"These have been entirely removed on other architectures, so let's
just do the same for ia32 and remove it unconditionally."

071929dbdd86 ("arm64: Stop printing the virtual memory layout")
1c31d4e96b8c ("ARM: 8820/1: mm: Stop printing the virtual memory layout")
31833332f798 ("m68k/mm: Stop printing the virtual memory layout")
fd8d0ca25631 ("parisc: Hide virtual kernel memory layout")
adb1fe9ae2ee ("mm/page_alloc: Remove kernel address exposure in free_reserved_area()")

Signed-off-by: Arvind Sankar <[e-mail]>
---
 arch/xtensa/mm/init.c | 46 -------------------------------------------
 1 file changed, 46 deletions(-)

Comments

Tycho Andersen March 5, 2020, 8:51 p.m. UTC | #1

On Thu, Mar 05, 2020 at 10:11:44AM -0500, Arvind Sankar wrote:
> For security, don't display the kernel's virtual memory layout.
> 
> Kees Cook points out:
> "These have been entirely removed on other architectures, so let's
> just do the same for ia32 and remove it unconditionally."
> 
> 071929dbdd86 ("arm64: Stop printing the virtual memory layout")
> 1c31d4e96b8c ("ARM: 8820/1: mm: Stop printing the virtual memory layout")
> 31833332f798 ("m68k/mm: Stop printing the virtual memory layout")
> fd8d0ca25631 ("parisc: Hide virtual kernel memory layout")
> adb1fe9ae2ee ("mm/page_alloc: Remove kernel address exposure in free_reserved_area()")
> 
> Signed-off-by: Arvind Sankar <[e-mail]>

Acked-by: Tycho Andersen <[e-mail]>

Max Filippov March 6, 2020, 7:54 a.m. UTC | #2

On Thu, Mar 5, 2020 at 7:11 AM Arvind Sankar <[e-mail]> wrote:
>
> For security, don't display the kernel's virtual memory layout.

Given that primary users of xtensa linux kernels are developers
removing this information, and even disabling it by default doesn't
sound reasonable to me.

Patch

diff --git a/arch/xtensa/mm/init.c b/arch/xtensa/mm/init.c
index 19c625e6d81f..7ba3f1fce8ec 100644
--- a/arch/xtensa/mm/init.c
+++ b/arch/xtensa/mm/init.c
@@ -155,52 +155,6 @@  void __init mem_init(void)
 	memblock_free_all();
 
 	mem_init_print_info(NULL);
-	pr_info("virtual kernel memory layout:\n"
-#ifdef CONFIG_KASAN
-		"    kasan   : 0x%08lx - 0x%08lx  (%5lu MB)\n"
-#endif
-#ifdef CONFIG_MMU
-		"    vmalloc : 0x%08lx - 0x%08lx  (%5lu MB)\n"
-#endif
-#ifdef CONFIG_HIGHMEM
-		"    pkmap   : 0x%08lx - 0x%08lx  (%5lu kB)\n"
-		"    fixmap  : 0x%08lx - 0x%08lx  (%5lu kB)\n"
-#endif
-		"    lowmem  : 0x%08lx - 0x%08lx  (%5lu MB)\n"
-		"    .text   : 0x%08lx - 0x%08lx  (%5lu kB)\n"
-		"    .rodata : 0x%08lx - 0x%08lx  (%5lu kB)\n"
-		"    .data   : 0x%08lx - 0x%08lx  (%5lu kB)\n"
-		"    .init   : 0x%08lx - 0x%08lx  (%5lu kB)\n"
-		"    .bss    : 0x%08lx - 0x%08lx  (%5lu kB)\n",
-#ifdef CONFIG_KASAN
-		KASAN_SHADOW_START, KASAN_SHADOW_START + KASAN_SHADOW_SIZE,
-		KASAN_SHADOW_SIZE >> 20,
-#endif
-#ifdef CONFIG_MMU
-		VMALLOC_START, VMALLOC_END,
-		(VMALLOC_END - VMALLOC_START) >> 20,
-#ifdef CONFIG_HIGHMEM
-		PKMAP_BASE, PKMAP_BASE + LAST_PKMAP * PAGE_SIZE,
-		(LAST_PKMAP*PAGE_SIZE) >> 10,
-		FIXADDR_START, FIXADDR_TOP,
-		(FIXADDR_TOP - FIXADDR_START) >> 10,
-#endif
-		PAGE_OFFSET, PAGE_OFFSET +
-		(max_low_pfn - min_low_pfn) * PAGE_SIZE,
-#else
-		min_low_pfn * PAGE_SIZE, max_low_pfn * PAGE_SIZE,
-#endif
-		((max_low_pfn - min_low_pfn) * PAGE_SIZE) >> 20,
-		(unsigned long)_text, (unsigned long)_etext,
-		(unsigned long)(_etext - _text) >> 10,
-		(unsigned long)__start_rodata, (unsigned long)__end_rodata,
-		(unsigned long)(__end_rodata - __start_rodata) >> 10,
-		(unsigned long)_sdata, (unsigned long)_edata,
-		(unsigned long)(_edata - _sdata) >> 10,
-		(unsigned long)__init_begin, (unsigned long)__init_end,
-		(unsigned long)(__init_end - __init_begin) >> 10,
-		(unsigned long)__bss_start, (unsigned long)__bss_stop,
-		(unsigned long)(__bss_stop - __bss_start) >> 10);
 }
 
 static void __init parse_memmap_one(char *p)