From: Joerg Roedel <[email protected]>
Backport commits from upstream to fix a data corruption
issue that gets exposed when using PTI on x86-32.
Please consider them for inclusion into stable-5.2.
Joerg Roedel (3):
x86/mm: Check for pfn instead of page in vmalloc_sync_one()
x86/mm: Sync also unmappings in vmalloc_sync_all()
mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()
arch/x86/mm/fault.c | 15 ++++++---------
mm/vmalloc.c | 9 +++++++++
2 files changed, 15 insertions(+), 9 deletions(-)
--
2.16.4
From: Joerg Roedel <[email protected]>
commit 3f8fd02b1bf1d7ba964485a56f2f4b53ae88c167 upstream.
On x86-32 with PTI enabled, parts of the kernel page-tables are not shared
between processes. This can cause mappings in the vmalloc/ioremap area to
persist in some page-tables after the region is unmapped and released.
When the region is re-used the processes with the old mappings do not fault
in the new mappings but still access the old ones.
This causes undefined behavior, in reality often data corruption, kernel
oopses and panics and even spontaneous reboots.
Fix this problem by activly syncing unmaps in the vmalloc/ioremap area to
all page-tables in the system before the regions can be re-used.
References: https://bugzilla.suse.com/show_bug.cgi?id=1118689
Fixes: 5d72b4fba40ef ('x86, mm: support huge I/O mapping capability I/F')
Signed-off-by: Joerg Roedel <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Dave Hansen <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
mm/vmalloc.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 0f76cca32a1c..080d30408ce3 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1213,6 +1213,12 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
if (unlikely(valist == NULL))
return false;
+ /*
+ * First make sure the mappings are removed from all page-tables
+ * before they are freed.
+ */
+ vmalloc_sync_all();
+
/*
* TODO: to calculate a flush range without looping.
* The list can be up to lazy_max_pages() elements.
@@ -3001,6 +3007,9 @@ EXPORT_SYMBOL(remap_vmalloc_range);
/*
* Implement a stub for vmalloc_sync_all() if the architecture chose not to
* have one.
+ *
+ * The purpose of this function is to make sure the vmalloc area
+ * mappings are identical in all page-tables in the system.
*/
void __weak vmalloc_sync_all(void)
{
--
2.16.4
On Tue, Aug 13, 2019 at 05:28:11PM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <[email protected]>
>
> Backport commits from upstream to fix a data corruption
> issue that gets exposed when using PTI on x86-32.
>
> Please consider them for inclusion into stable-5.2.
Thanks for these. Based on the Fixes: tags on the commits, I've taken
them all the way back to 4.4.y.
greg k-h
Hi Greg,
On Tue, Aug 13, 2019 at 08:36:42PM +0200, Greg Kroah-Hartman wrote:
> On Tue, Aug 13, 2019 at 05:28:11PM +0200, Joerg Roedel wrote:
> > From: Joerg Roedel <[email protected]>
> >
> > Backport commits from upstream to fix a data corruption
> > issue that gets exposed when using PTI on x86-32.
> >
> > Please consider them for inclusion into stable-5.2.
>
> Thanks for these. Based on the Fixes: tags on the commits, I've taken
> them all the way back to 4.4.y.
Thank you! The problem almost only exposes itself when PTI on x86-32 is
enabled (which was merged in 4.19), so I only backported down to that
kernel.
But it is right that it might be possible to trigger the problem on
older kernels too, e.g. in some 32bit XEN-pv configurations that use
same PAE page-table structures as the PTI code for 32bit.
So thanks for picking the fixes up for the older kernels too.
Regards,
Joerg