linux-kernel - Re: early fixmap causes kmap breakage

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20081230075428.GC14132@wotan.suse.de>
Date:	Tue, 30 Dec 2008 08:54:28 +0100
From:	Nick Piggin <npiggin@...e.de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, ebiederm@...ssion.com,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	ijc@...lion.org.uk
Subject: Re: early fixmap causes kmap breakage

On Tue, Dec 30, 2008 at 07:13:44AM +0100, Ingo Molnar wrote:
> 
> * Nick Piggin <npiggin@...e.de> wrote:
> 
> > On Mon, Dec 29, 2008 at 03:17:31PM -0800, Andrew Morton wrote:
> > > On Thu, 18 Dec 2008 22:15:43 +0100
> > > Nick Piggin <npiggin@...e.de> wrote:
> > > 
> > > > Hi,
> > > > 
> > > > I've debugged a problem where i386+pae systems with more than a few CPUs
> > > > blow up at boot in the kmap_atomic code.
> > > 
> > > ping?
> > 
> > No further progress here, I'm waiting on input for how to fix this 
> > "nicely". Meantime, clearing the early fixmap pte I guess works, but you 
> > lose a page... is it possible to put it into .initdata or is there some 
> > issue with that? (I guess on a PAE kernel, 4K isn't a big deal).
> 
> yeah, 4K shouldnt be a big deal. Mind sending a patch for this?

I don't know if we should put a warning when we encounter this condition,
to help catch other unintended uses...

But this at least clears out the early fixmap pte and provides a contiguous
allocation...

---
 arch/x86/mm/init_32.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

Index: linux-2.6/arch/x86/mm/init_32.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init_32.c
+++ linux-2.6/arch/x86/mm/init_32.c
@@ -155,6 +155,7 @@ page_table_range_init(unsigned long star
 	unsigned long vaddr;
 	pgd_t *pgd;
 	pmd_t *pmd;
+	pte_t *lastpte = NULL;
 
 	vaddr = start;
 	pgd_idx = pgd_index(vaddr);
@@ -166,7 +167,19 @@ page_table_range_init(unsigned long star
 		pmd = pmd + pmd_index(vaddr);
 		for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end);
 							pmd++, pmd_idx++) {
-			one_page_table_init(pmd);
+			pte_t *pte;
+
+			pte = one_page_table_init(pmd);
+			if (lastpte && lastpte + PTRS_PER_PTE != pte) {
+				pte_t *newpte;
+
+				pmd_clear(pmd);
+				newpte = one_page_table_init(pmd);
+				BUG_ON(lastpte + PTRS_PER_PTE != newpte);
+				memset(newpte, pte, PAGE_SIZE);
+				pte = lastpte;
+			}
+			lastpte = pte;
 
 			vaddr += PMD_SIZE;
 		}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/