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| author | Andrew Cooper <andrew.cooper3@citrix.com> | 2013-10-04 12:24:34 +0200 |
|---|---|---|
| committer | Jan Beulich <jbeulich@suse.com> | 2013-10-04 12:24:34 +0200 |
| commit | 7cfb0053629c4dd1a6f01dc43cca7c0c25b8b7bf (patch) | |
| tree | 601e6c122d3e3f97c8da982a28db16f27e9bfba5 | |
| parent | 0aa27ce3351f7eb09d13e863a1d5f303086aa32a (diff) | |
| download | xen-7cfb0053629c4dd1a6f01dc43cca7c0c25b8b7bf.tar.gz xen-7cfb0053629c4dd1a6f01dc43cca7c0c25b8b7bf.tar.bz2 xen-7cfb0053629c4dd1a6f01dc43cca7c0c25b8b7bf.zip | |
x86/percpu: Force INVALID_PERCPU_AREA into the non-canonical address region
This causes accidental uses of per_cpu() on a pcpu with an INVALID_PERCPU_AREA
to result in a #GF for attempting to access the middle of the non-canonical
virtual address region.
This is preferable to the current behaviour, where incorrect use of per_cpu()
will result in an effective NULL structure dereference which has security
implication in the context of PV guests.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
| -rw-r--r-- | xen/arch/x86/percpu.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/xen/arch/x86/percpu.c b/xen/arch/x86/percpu.c index e5450248ad..1c1dad9011 100644 --- a/xen/arch/x86/percpu.c +++ b/xen/arch/x86/percpu.c @@ -6,7 +6,14 @@ #include <xen/rcupdate.h> unsigned long __per_cpu_offset[NR_CPUS]; -#define INVALID_PERCPU_AREA (-(long)__per_cpu_start) + +/* + * Force uses of per_cpu() with an invalid area to attempt to access the + * middle of the non-canonical address space resulting in a #GP, rather than a + * possible #PF at (NULL + a little) which has security implications in the + * context of PV guests. + */ +#define INVALID_PERCPU_AREA (0x8000000000000000L - (long)__per_cpu_start) #define PERCPU_ORDER (get_order_from_bytes(__per_cpu_data_end-__per_cpu_start)) void __init percpu_init_areas(void) |