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| author | Dave Hansen <dave.hansen@linux.intel.com> | 2018-04-06 22:55:14 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-04-12 09:05:59 +0200 |
| commit | 639d6aafe437a7464399d2a77d006049053df06f (patch) | |
| tree | 5f8fa30d1ae8e8713075a289bf473331dc1c9b75 /arch | |
| parent | x86/mm: Comment _PAGE_GLOBAL mystery (diff) | |
| download | linux-639d6aafe437a7464399d2a77d006049053df06f.tar.xz linux-639d6aafe437a7464399d2a77d006049053df06f.zip | |
x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init
__ro_after_init data gets stuck in the .rodata section. That's normally
fine because the kernel itself manages the R/W properties.
But, if we run __change_page_attr() on an area which is __ro_after_init,
the .rodata checks will trigger and force the area to be immediately
read-only, even if it is early-ish in boot. This caused problems when
trying to clear the _PAGE_GLOBAL bit for these area in the PTI code:
it cleared _PAGE_GLOBAL like I asked, but also took it up on itself
to clear _PAGE_RW. The kernel then oopses the next time it wrote to
a __ro_after_init data structure.
To fix this, add the kernel_set_to_readonly check, just like we have
for kernel text, just a few lines below in this function.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180406205514.8D898241@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/mm/pageattr.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 968f51a2e39b..a7324045d87d 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -298,9 +298,11 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address, /* * The .rodata section needs to be read-only. Using the pfn - * catches all aliases. + * catches all aliases. This also includes __ro_after_init, + * so do not enforce until kernel_set_to_readonly is true. */ - if (within(pfn, __pa_symbol(__start_rodata) >> PAGE_SHIFT, + if (kernel_set_to_readonly && + within(pfn, __pa_symbol(__start_rodata) >> PAGE_SHIFT, __pa_symbol(__end_rodata) >> PAGE_SHIFT)) pgprot_val(forbidden) |= _PAGE_RW; |