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author | Dave Hansen <dave.hansen@linux.intel.com> | 2018-04-20 15:20:23 -0700 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2018-04-25 11:02:50 +0200 |
commit | a44ca8f5a30c008b54d07b00eed4eae7f169fcd0 (patch) | |
tree | a40b7e227a235a60a9b26dd42820e4e937f93638 /arch/x86 | |
parent | 58e65b51e6f9b9dd94a25ff2b2772222e0358099 (diff) | |
download | linux-stable-a44ca8f5a30c008b54d07b00eed4eae7f169fcd0.tar.gz linux-stable-a44ca8f5a30c008b54d07b00eed4eae7f169fcd0.tar.bz2 linux-stable-a44ca8f5a30c008b54d07b00eed4eae7f169fcd0.zip |
x86/pti: Reduce amount of kernel text allowed to be Global
commit abb67605203687c8b7943d760638d0301787f8d9
Kees reported to me that I made too much of the kernel image global.
It was far more than just text:
I think this is too much set global: _end is after data,
bss, and brk, and all kinds of other stuff that could
hold secrets. I think this should match what
mark_rodata_ro() is doing.
This does exactly that. We use __end_rodata_hpage_align as our
marker both because it is huge-page-aligned and it does not contain
any sections we expect to hold secrets.
Kees's logic was that r/o data is in the kernel image anyway and,
in the case of traditional distributions, can be freely downloaded
from the web, so there's no reason to hide it.
Fixes: 8c06c7740 (x86/pti: Leave kernel text global for !PCID)
Reported-by: Kees Cook <keescook@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: https://lkml.kernel.org/r/20180420222023.1C8B2B20@viggo.jf.intel.com
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/mm/pti.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index f1fd52f449e0..ae3eb4f5d53b 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -430,12 +430,24 @@ static inline bool pti_kernel_image_global_ok(void) */ void pti_clone_kernel_text(void) { + /* + * rodata is part of the kernel image and is normally + * readable on the filesystem or on the web. But, do not + * clone the areas past rodata, they might contain secrets. + */ unsigned long start = PFN_ALIGN(_text); - unsigned long end = ALIGN((unsigned long)_end, PMD_PAGE_SIZE); + unsigned long end = (unsigned long)__end_rodata_hpage_align; if (!pti_kernel_image_global_ok()) return; + pr_debug("mapping partial kernel image into user address space\n"); + + /* + * Note that this will undo _some_ of the work that + * pti_set_kernel_image_nonglobal() did to clear the + * global bit. + */ pti_clone_pmds(start, end, _PAGE_RW); } @@ -458,8 +470,6 @@ void pti_set_kernel_image_nonglobal(void) if (pti_kernel_image_global_ok()) return; - pr_debug("set kernel image non-global\n"); - set_memory_nonglobal(start, (end - start) >> PAGE_SHIFT); } |