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From: Andy Lutomirski <luto@kernel.org>
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	x86@kernel.org, Borislav Petkov <bp@alien8.de>
Cc: Nadav Amit <nadav.amit@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	Brian Gerst <brgerst@gmail.com>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Andy Lutomirski <luto@kernel.org>
Subject: [kernel-hardening] [PATCH 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated
Date: Wed, 15 Jun 2016 17:28:24 -0700
Message-ID: <832aa0209ca4bd94b043add243ac36ab56285639.1466036668.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1466036668.git.luto@kernel.org>
In-Reply-To: <cover.1466036668.git.luto@kernel.org>

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
entry.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 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;
 	}
-- 
2.7.4

  parent reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-16  0:28 [kernel-hardening] [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski
2016-06-16  0:28 ` [kernel-hardening] [PATCH 01/13] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski
2016-06-16  0:28 ` Andy Lutomirski [this message]
2016-06-16  0:28 ` [kernel-hardening] [PATCH 03/13] x86/cpa: Warn if kernel_unmap_pages_in_pgd is used inappropriately Andy Lutomirski
2016-06-16  0:28 ` [kernel-hardening] [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of number of stacks Andy Lutomirski
2016-06-16 11:10   ` [kernel-hardening] " Vladimir Davydov
2016-06-16 17:21     ` Andy Lutomirski
2016-06-16 19:20       ` Andy Lutomirski
2016-06-16 15:33   ` Josh Poimboeuf
2016-06-16 17:39     ` Andy Lutomirski
2016-06-16 19:39       ` Josh Poimboeuf
2016-06-16  0:28 ` [kernel-hardening] [PATCH 05/13] mm: Move memcg stack accounting to account_kernel_stack Andy Lutomirski
2016-06-16  0:28 ` [kernel-hardening] [PATCH 06/13] fork: Add generic vmalloced stack support Andy Lutomirski
2016-06-16 17:25   ` [kernel-hardening] " Kees Cook
2016-06-16 17:37     ` Andy Lutomirski
2016-06-16  0:28 ` [kernel-hardening] [PATCH 07/13] x86/die: Don't try to recover from an OOPS on a non-default stack Andy Lutomirski
2016-06-16  0:28 ` [kernel-hardening] [PATCH 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Andy Lutomirski
2016-06-16 17:50   ` [kernel-hardening] " Josh Poimboeuf
2016-06-16 17:57     ` Andy Lutomirski
2016-06-16  0:28 ` [kernel-hardening] [PATCH 09/13] x86/dumpstack: When dumping stack bytes due to OOPS, start with regs->sp Andy Lutomirski
2016-06-16 11:56   ` [kernel-hardening] " Borislav Petkov
2016-06-16  0:28 ` [kernel-hardening] [PATCH 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski
2016-06-16 18:16   ` [kernel-hardening] " Josh Poimboeuf
2016-06-16 18:22     ` Andy Lutomirski
2016-06-16 18:33       ` Josh Poimboeuf
2016-06-16 18:37         ` Andy Lutomirski
2016-06-16 18:54           ` Josh Poimboeuf
2016-06-16  0:28 ` [kernel-hardening] [PATCH 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski
2016-06-16  0:28 ` [kernel-hardening] [PATCH 12/13] x86/mm/64: Enable vmapped stacks Andy Lutomirski
2016-06-16  4:17   ` [kernel-hardening] " Mika Penttilä
2016-06-16  5:33     ` Andy Lutomirski
2016-06-16 13:11       ` Rik van Riel
2016-06-16  0:28 ` [kernel-hardening] [PATCH 13/13] x86/mm: Improve stack-overflow #PF handling Andy Lutomirski
2016-06-16  6:05 ` [kernel-hardening] Re: [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Heiko Carstens
2016-06-16 17:50   ` Andy Lutomirski
2016-06-16 18:14     ` Andy Lutomirski
2016-06-16 21:27       ` Andy Lutomirski
2016-06-17  3:58   ` Andy Lutomirski
2016-06-17  7:27     ` Heiko Carstens
2016-06-17 17:38       ` Andy Lutomirski
2016-06-20  5:58         ` Heiko Carstens
2016-06-20  6:01           ` Andy Lutomirski
2016-06-20  7:07             ` Heiko Carstens
2016-06-16 17:24 ` Kees Cook

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