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Date: Tue, 21 Aug 2018 01:16:26 +0000 From: Bin Yang <bin.yang@...el.com> To: tglx@...utronix.de, mingo@...nel.org, hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org, peterz@...radead.org, dave.hansen@...el.com, mark.gross@...el.com, bin.yang@...el.com Subject: [PATCH v3 5/5] x86/mm: add WARN_ON_ONCE() for wrong large page mapping If there is a large page which contains an area which requires a different mapping that the one which the large page provides, then something went wrong _before_ this code is called. Here we can catch a case where the existing mapping is wrong already. Inspired-by: Thomas Gleixner <tglx@...utronix.de> Signed-off-by: Bin Yang <bin.yang@...el.com> --- arch/x86/mm/pageattr.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index fd90c5b..91a250c 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -625,6 +625,7 @@ try_preserve_large_page(pte_t *kpte, unsigned long address, psize = page_level_size(level); pmask = page_level_mask(level); + addr = address & pmask; /* * Calculate the number of pages, which fit into this large @@ -636,6 +637,12 @@ try_preserve_large_page(pte_t *kpte, unsigned long address, cpa->numpages = numpages; /* + * The old pgprot should not have any protection bit. Otherwise, + * the existing mapping is wrong already. + */ + WARN_ON_ONCE(needs_static_protections(old_prot, addr, psize, old_pfn)); + + /* * We are safe now. Check whether the new pgprot is the same: * Convert protection attributes to 4k-format, as cpa->mask* are set * up accordingly. @@ -690,7 +697,6 @@ try_preserve_large_page(pte_t *kpte, unsigned long address, * would anyway result in a split after doing all the check work * for nothing. */ - addr = address & pmask; if (address != addr || cpa->numpages != numpages) goto out_unlock; -- 2.7.4
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