Commit-ID: efad2b4151521c944e405272035a673c74125c65 Gitweb: https://git.kernel.org/tip/efad2b4151521c944e405272035a673c74125c65 Author: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> AuthorDate: Fri, 6 Apr 2018 13:55:14 -0700 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Mon, 9 Apr 2018 18:27:34 +0200 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@xxxxxxxxxxxxxxx> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Juergen Gross <jgross@xxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Nadav Amit <namit@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: linux-mm@xxxxxxxxx Link: http://lkml.kernel.org/r/20180406205514.8D898241@xxxxxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/mm/pageattr.c | 6 ++++-- 1 file 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; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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