linux-kernel - mmu_notifier: close hole in fork

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: <Pine.LNX.4.64.0801311355260.27804@schroedinger.engr.sgi.com>
Date:	Thu, 31 Jan 2008 14:01:43 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Andrea Arcangeli <andrea@...ranet.com>
cc:	Robin Holt <holt@....com>, Avi Kivity <avi@...ranet.com>,
	Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: mmu_notifier: close hole in fork

Talking to Robin and Jack we found taht we still have a hole during fork. 
Fork may set a pte writeprotect. At that point the remote pte are 
not marked readonly(!). Remote writes may occur to pages that are marked 
readonly locally without this patch.

mmu_notifier: Provide invalidate_range on fork

On fork we change ptes in cow mappings to readonly. This means we must
invalidate the ptes so that they are reestablished later with proper
permission.

Signed-off-by: Christoph Lameter <clameter@....com>

---
 mm/memory.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c	2008-01-31 13:42:35.000000000 -0800
+++ linux-2.6/mm/memory.c	2008-01-31 13:47:31.000000000 -0800
@@ -602,6 +602,9 @@ int copy_page_range(struct mm_struct *ds
 	if (is_vm_hugetlb_page(vma))
 		return copy_hugetlb_page_range(dst_mm, src_mm, vma);
 
+	if (is_cow_mapping(vma->vm_flags))
+		mmu_notifier(invalidate_range_begin, src_mm, addr, end, 0);
+
 	dst_pgd = pgd_offset(dst_mm, addr);
 	src_pgd = pgd_offset(src_mm, addr);
 	do {
@@ -612,6 +615,9 @@ int copy_page_range(struct mm_struct *ds
 						vma, addr, next))
 			return -ENOMEM;
 	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
+
+	if (is_cow_mapping(vma->vm_flags))
+		mmu_notifier(invalidate_range_end, src_mm, 0);
 	return 0;
 }
 
--
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/