4.14-stable review patch. If anyone has any objections, please let me know.
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From: Jason Andryuk jandryuk@gmail.com
commit 36104cb9012a82e73c32a3b709257766b16bcd1d upstream.
Commit 2cc42bac1c79 ("x86-64/Xen: eliminate W+X mappings") introduced a call to get_cpu_cap, which is fstack-protected. This is works on x86-64 as commit 4f277295e54c ("x86/xen: init %gs very early to avoid page faults with stack protector") ensures the stack protector is configured, but it it did not cover x86-32.
Delay calling get_cpu_cap until after xen_setup_gdt has initialized the stack canary. Without this, a 32bit PV machine crashes early in boot. (XEN) Domain 0 (vcpu#0) crashed on cpu#0: (XEN) ----[ Xen-4.6.6-xc x86_64 debug=n Tainted: C ]---- (XEN) CPU: 0 (XEN) RIP: e019:[<00000000c10362f8>]
And the PV kernel IP corresponds to init_scattered_cpuid_features 0xc10362f8 <+24>: mov %gs:0x14,%eax
Fixes 2cc42bac1c79 ("x86-64/Xen: eliminate W+X mappings")
Signed-off-by: Jason Andryuk jandryuk@gmail.com Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Signed-off-by: Boris Ostrovsky boris.ostrovsky@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/xen/enlighten_pv.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1258,10 +1258,6 @@ asmlinkage __visible void __init xen_sta */ __userpte_alloc_gfp &= ~__GFP_HIGHMEM;
- /* Work out if we support NX */ - get_cpu_cap(&boot_cpu_data); - x86_configure_nx(); - /* Get mfn list */ xen_build_dynamic_phys_to_machine();
@@ -1271,6 +1267,10 @@ asmlinkage __visible void __init xen_sta */ xen_setup_gdt(0);
+ /* Work out if we support NX */ + get_cpu_cap(&boot_cpu_data); + x86_configure_nx(); + xen_init_irq_ops();
/* Let's presume PV guests always boot on vCPU with id 0. */