linux-kernel - [RFC] remap_pfn_range: store vm_pgoff for all linear_over_vma

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-next>] [day] [month] [year] [list]

Message-ID: <20081023220913.GA20300@linux-os.sc.intel.com>
Date:	Thu, 23 Oct 2008 15:09:14 -0700
From:	Venki Pallipadi <venkatesh.pallipadi@...el.com>
To:	npiggin@...e.de, hugh@...itas.com
Cc:	apkm@...ux-os.sc.intel.com, Ingo Molnar <mingo@...e.hu>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [RFC] remap_pfn_range: store vm_pgoff for all linear_over_vma_region mappings


While working on x86 PAT, we are having some hurdles with tracking
remap_pfn_range() regions, as later we do not have any information to say
whether that PFNMAP mapping is linear for the entire vma range or
it is smaller granularity regions within the vma.

A simple solution to this is to use vm_pgoff as an indicator for
linear mapping over the vma region. Currently, remap_pfn_range
only sets vm_pgoff only for COW mappings. Below patch changes the
logic and sets the vm_pgoff irrespective of COW.

>From our understanding of the code, this should not break anyone.
Just sending it as an RFC to get feedback on whether it is OK to do
something like this or are there any corner cases that we may
break or watch out for.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>

---
 mm/memory.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c	2008-10-21 09:58:47.000000000 -0700
+++ linux-2.6/mm/memory.c	2008-10-23 13:38:26.000000000 -0700
@@ -1575,11 +1575,10 @@ int remap_pfn_range(struct vm_area_struc
 	 * behaviour that some programs depend on. We mark the "original"
 	 * un-COW'ed pages by matching them up with "vma->vm_pgoff".
 	 */
-	if (is_cow_mapping(vma->vm_flags)) {
-		if (addr != vma->vm_start || end != vma->vm_end)
-			return -EINVAL;
+	if (addr == vma->vm_start && end == vma->vm_end)
 		vma->vm_pgoff = pfn;
-	}
+	else if (is_cow_mapping(vma->vm_flags))
+		return -EINVAL;
 
 	vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
 
--
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/