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Date: Fri, 17 Jun 2016 13:00:38 -0700
From: Andy Lutomirski <>
	Borislav Petkov <>,
	Nadav Amit <>,
	Kees Cook <>,
	Brian Gerst <>,
	"" <>,
	Linus Torvalds <>,
	Josh Poimboeuf <>,
	Jann Horn <>,
	Heiko Carstens <>,
	Andy Lutomirski <>
Subject: [PATCH v2 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated

This avoids pointless races in which another CPU or task might see a
partially populated global pgd entry.  These races should normally
be harmless, but, if another CPU propagates the entry via
vmalloc_fault and then populate_pgd fails (due to memory allocation
failure, for example), this prevents a use-after-free of the pgd

Signed-off-by: Andy Lutomirski <>
 arch/x86/mm/pageattr.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 7a1f7bbf4105..6a8026918bf6 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1113,7 +1113,9 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	ret = populate_pud(cpa, addr, pgd_entry, pgprot);
 	if (ret < 0) {
-		unmap_pgd_range(cpa->pgd, addr,
+		if (pud)
+			free_page((unsigned long)pud);
+		unmap_pud_range(pgd_entry, addr,
 				addr + (cpa->numpages << PAGE_SHIFT));
 		return ret;

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