[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.2] x86/percpu: Force INVALID_PERCPU_AREA into the non-canonical address region
commit 707aec94c54127ebfda7d0f8455ecbb332ee49f0 Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> AuthorDate: Tue Oct 22 12:04:01 2013 +0200 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Tue Oct 22 12:04:01 2013 +0200 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@xxxxxxxxxx> Acked-by: Keir Fraser <keir@xxxxxxx> master commit: 7cfb0053629c4dd1a6f01dc43cca7c0c25b8b7bf master date: 2013-10-04 12:24:34 +0200 --- 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 e545024..1c1dad9 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) -- generated by git-patchbot for /home/xen/git/xen.git#stable-4.2 _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxx http://lists.xensource.com/xen-changelog
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