@@ -57,4 +57,6 @@ static inline bool xen_x2apic_para_available(void)
}
#endif
+extern void xen_set_iopl_mask(unsigned mask);
+
#endif /* _ASM_X86_XEN_HYPERVISOR_H */
@@ -48,6 +48,7 @@
#include <asm/syscalls.h>
#include <asm/debugreg.h>
#include <asm/switch_to.h>
+#include <asm/xen/hypervisor.h>
asmlinkage extern void ret_from_fork(void);
@@ -417,6 +418,17 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV))
__switch_to_xtra(prev_p, next_p, tss);
+#ifdef CONFIG_XEN
+ /*
+ * On Xen PV, IOPL bits in pt_regs->flags have no effect, and
+ * current_pt_regs()->flags may not match the current task's
+ * intended IOPL. We need to switch it manually.
+ */
+ if (unlikely(xen_pv_domain() &&
+ prev->iopl != next->iopl))
+ xen_set_iopl_mask(next->iopl);
+#endif
+
if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) {
/*
* AMD CPUs have a misfeature: SYSRET sets the SS selector but
@@ -959,7 +959,7 @@ static void xen_load_sp0(struct tss_struct *tss,
tss->x86_tss.sp0 = thread->sp0;
}
-static void xen_set_iopl_mask(unsigned mask)
+void xen_set_iopl_mask(unsigned mask)
{
struct physdev_set_iopl set_iopl;
This is a note to let you know that I have just added a patch titled x86/iopl/64: Properly context-switch IOPL on Xen PV to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue This patch is scheduled to be released in version 4.2.8-ckt7. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 4.2.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ---8<------------------------------------------------------------ From 440b7e60f79c3673b0112882db09a2ce73b08035 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski <luto@kernel.org> Date: Wed, 16 Mar 2016 14:14:21 -0700 Subject: x86/iopl/64: Properly context-switch IOPL on Xen PV commit b7a584598aea7ca73140cb87b40319944dd3393f upstream. On Xen PV, regs->flags doesn't reliably reflect IOPL and the exit-to-userspace code doesn't change IOPL. We need to context switch it manually. I'm doing this without going through paravirt because this is specific to Xen PV. After the dust settles, we can merge this with the 32-bit code, tidy up the iopl syscall implementation, and remove the set_iopl pvop entirely. Fixes XSA-171. Reviewewd-by: Jan Beulich <JBeulich@suse.com> Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jan Beulich <JBeulich@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/693c3bd7aeb4d3c27c92c622b7d0f554a458173c.1458162709.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> [ kamal: backport to 4.2-stable: no X86_FEATURE_XENPV so just call xen_pv_domain() directly ] Acked-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/x86/include/asm/xen/hypervisor.h | 2 ++ arch/x86/kernel/process_64.c | 12 ++++++++++++ arch/x86/xen/enlighten.c | 2 +- 3 files changed, 15 insertions(+), 1 deletion(-) -- 2.7.4