From: Greg Kroah-Hartman <gregkh@suse.de>
Date: Wed, 18 Aug 2010 01:11:44 +0000 (-0700)
Subject: another .27 patch
X-Git-Tag: v2.6.27.52~9
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=fb18d338fdf470b503d3f54a2153b1c6e910f933;p=thirdparty%2Fkernel%2Fstable-queue.git

another .27 patch
---

diff --git a/review-2.6.27/mm-fix-page-table-unmap-for-stack-guard-page-properly.patch b/review-2.6.27/mm-fix-page-table-unmap-for-stack-guard-page-properly.patch
new file mode 100644
index 00000000000..44129cbaaa2
--- /dev/null
+++ b/review-2.6.27/mm-fix-page-table-unmap-for-stack-guard-page-properly.patch
@@ -0,0 +1,64 @@
+From 11ac552477e32835cb6970bf0a70c210807f5673 Mon Sep 17 00:00:00 2001
+From: Linus Torvalds <torvalds@linux-foundation.org>
+Date: Sat, 14 Aug 2010 11:44:56 -0700
+Subject: mm: fix page table unmap for stack guard page properly
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: Linus Torvalds <torvalds@linux-foundation.org>
+
+commit 11ac552477e32835cb6970bf0a70c210807f5673 upstream.
+
+We do in fact need to unmap the page table _before_ doing the whole
+stack guard page logic, because if it is needed (mainly 32-bit x86 with
+PAE and CONFIG_HIGHPTE, but other architectures may use it too) then it
+will do a kmap_atomic/kunmap_atomic.
+
+And those kmaps will create an atomic region that we cannot do
+allocations in.  However, the whole stack expand code will need to do
+anon_vma_prepare() and vma_lock_anon_vma() and they cannot do that in an
+atomic region.
+
+Now, a better model might actually be to do the anon_vma_prepare() when
+_creating_ a VM_GROWSDOWN segment, and not have to worry about any of
+this at page fault time.  But in the meantime, this is the
+straightforward fix for the issue.
+
+See https://bugzilla.kernel.org/show_bug.cgi?id=16588 for details.
+
+Reported-by: Wylda <wylda@volny.cz>
+Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
+Reported-by: Mike Pagano <mpagano@gentoo.org>
+Reported-by: François Valenduc <francois.valenduc@tvcablenet.be>
+Tested-by: Ed Tomlinson <edt@aei.ca>
+Cc: Pekka Enberg <penberg@kernel.org>
+Cc: Greg KH <gregkh@suse.de>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
+
+---
+ mm/memory.c |    9 ++++-----
+ 1 file changed, 4 insertions(+), 5 deletions(-)
+
+--- a/mm/memory.c
++++ b/mm/memory.c
+@@ -2428,14 +2428,13 @@ static int do_anonymous_page(struct mm_s
+ 	spinlock_t *ptl;
+ 	pte_t entry;
+ 
+-	if (check_stack_guard_page(vma, address) < 0) {
+-		pte_unmap(page_table);
++	pte_unmap(page_table);
++
++	/* Check if we need to add a guard page to the stack */
++	if (check_stack_guard_page(vma, address) < 0)
+ 		return VM_FAULT_SIGBUS;
+-	}
+ 
+ 	/* Allocate our own private page. */
+-	pte_unmap(page_table);
+-
+ 	if (unlikely(anon_vma_prepare(vma)))
+ 		goto oom;
+ 	page = alloc_zeroed_user_highpage_movable(vma, address);
diff --git a/review-2.6.27/series b/review-2.6.27/series
index 7c26ef1fcb3..cc279ed03ef 100644
--- a/review-2.6.27/series
+++ b/review-2.6.27/series
@@ -2,3 +2,4 @@ mm-keep-a-guard-page-below-a-grow-down-stack-segment.patch
 mm-fix-missing-page-table-unmap-for-stack-guard-page-failure-case.patch
 x86-don-t-send-sigbus-for-kernel-page-faults.patch
 mm-pass-correct-mm-when-growing-stack.patch
+mm-fix-page-table-unmap-for-stack-guard-page-properly.patch