[Focal][CVE-2020-15852][PATCH] x86/ioperm: Fix io bitmap invalidation on Xen PV
William Breathitt Gray
william.gray at canonical.com
Wed Aug 12 14:11:06 UTC 2020
From: Andy Lutomirski <luto at kernel.org>
tss_invalidate_io_bitmap() wasn't wired up properly through the pvop
machinery, so the TSS and Xen's io bitmap would get out of sync
whenever disabling a valid io bitmap.
Add a new pvop for tss_invalidate_io_bitmap() to fix it.
This is XSA-329.
Fixes: 22fe5b0439dd ("x86/ioperm: Move TSS bitmap update to exit to user work")
Signed-off-by: Andy Lutomirski <luto at kernel.org>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Reviewed-by: Juergen Gross <jgross at suse.com>
Reviewed-by: Thomas Gleixner <tglx at linutronix.de>
Cc: stable at vger.kernel.org
Link: https://lkml.kernel.org/r/d53075590e1f91c19f8af705059d3ff99424c020.1595030016.git.luto@kernel.org
CVE-2020-15852
(cherry picked from commit cadfad870154e14f745ec845708bc17d166065f2)
Signed-off-by: William Breathitt Gray <william.gray at canonical.com>
---
arch/x86/include/asm/io_bitmap.h | 16 ++++++++++++++++
arch/x86/include/asm/paravirt.h | 5 +++++
arch/x86/include/asm/paravirt_types.h | 1 +
arch/x86/kernel/paravirt.c | 3 ++-
arch/x86/kernel/process.c | 18 ++----------------
arch/x86/xen/enlighten_pv.c | 12 ++++++++++++
6 files changed, 38 insertions(+), 17 deletions(-)
diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index ac1a99ffbd8d..7f080f5c7def 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -19,12 +19,28 @@ struct task_struct;
void io_bitmap_share(struct task_struct *tsk);
void io_bitmap_exit(struct task_struct *tsk);
+static inline void native_tss_invalidate_io_bitmap(void)
+{
+ /*
+ * Invalidate the I/O bitmap by moving io_bitmap_base outside the
+ * TSS limit so any subsequent I/O access from user space will
+ * trigger a #GP.
+ *
+ * This is correct even when VMEXIT rewrites the TSS limit
+ * to 0x67 as the only requirement is that the base points
+ * outside the limit.
+ */
+ this_cpu_write(cpu_tss_rw.x86_tss.io_bitmap_base,
+ IO_BITMAP_OFFSET_INVALID);
+}
+
void native_tss_update_io_bitmap(void);
#ifdef CONFIG_PARAVIRT_XXL
#include <asm/paravirt.h>
#else
#define tss_update_io_bitmap native_tss_update_io_bitmap
+#define tss_invalidate_io_bitmap native_tss_invalidate_io_bitmap
#endif
#else
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 694d8daf4983..0296dd66c167 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -296,6 +296,11 @@ static inline void write_idt_entry(gate_desc *dt, int entry, const gate_desc *g)
}
#ifdef CONFIG_X86_IOPL_IOPERM
+static inline void tss_invalidate_io_bitmap(void)
+{
+ PVOP_VCALL0(cpu.invalidate_io_bitmap);
+}
+
static inline void tss_update_io_bitmap(void)
{
PVOP_VCALL0(cpu.update_io_bitmap);
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 732f62e04ddb..8dfcb2508e6d 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -141,6 +141,7 @@ struct pv_cpu_ops {
void (*load_sp0)(unsigned long sp0);
#ifdef CONFIG_X86_IOPL_IOPERM
+ void (*invalidate_io_bitmap)(void);
void (*update_io_bitmap)(void);
#endif
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index c131ba4e70ef..97b4ce839b4c 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -343,7 +343,8 @@ struct paravirt_patch_template pv_ops = {
.cpu.swapgs = native_swapgs,
#ifdef CONFIG_X86_IOPL_IOPERM
- .cpu.update_io_bitmap = native_tss_update_io_bitmap,
+ .cpu.invalidate_io_bitmap = native_tss_invalidate_io_bitmap,
+ .cpu.update_io_bitmap = native_tss_update_io_bitmap,
#endif
.cpu.start_context_switch = paravirt_nop,
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 3d88300ec306..070383626d7f 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -323,20 +323,6 @@ void arch_setup_new_exec(void)
}
#ifdef CONFIG_X86_IOPL_IOPERM
-static inline void tss_invalidate_io_bitmap(struct tss_struct *tss)
-{
- /*
- * Invalidate the I/O bitmap by moving io_bitmap_base outside the
- * TSS limit so any subsequent I/O access from user space will
- * trigger a #GP.
- *
- * This is correct even when VMEXIT rewrites the TSS limit
- * to 0x67 as the only requirement is that the base points
- * outside the limit.
- */
- tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
-}
-
static inline void switch_to_bitmap(unsigned long tifp)
{
/*
@@ -347,7 +333,7 @@ static inline void switch_to_bitmap(unsigned long tifp)
* user mode.
*/
if (tifp & _TIF_IO_BITMAP)
- tss_invalidate_io_bitmap(this_cpu_ptr(&cpu_tss_rw));
+ tss_invalidate_io_bitmap();
}
static void tss_copy_io_bitmap(struct tss_struct *tss, struct io_bitmap *iobm)
@@ -381,7 +367,7 @@ void native_tss_update_io_bitmap(void)
u16 *base = &tss->x86_tss.io_bitmap_base;
if (!test_thread_flag(TIF_IO_BITMAP)) {
- tss_invalidate_io_bitmap(tss);
+ native_tss_invalidate_io_bitmap();
return;
}
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 507f4fb88fa7..9621d31104b6 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -841,6 +841,17 @@ static void xen_load_sp0(unsigned long sp0)
}
#ifdef CONFIG_X86_IOPL_IOPERM
+static void xen_invalidate_io_bitmap(void)
+{
+ struct physdev_set_iobitmap iobitmap = {
+ .bitmap = 0,
+ .nr_ports = 0,
+ };
+
+ native_tss_invalidate_io_bitmap();
+ HYPERVISOR_physdev_op(PHYSDEVOP_set_iobitmap, &iobitmap);
+}
+
static void xen_update_io_bitmap(void)
{
struct physdev_set_iobitmap iobitmap;
@@ -1070,6 +1081,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
.load_sp0 = xen_load_sp0,
#ifdef CONFIG_X86_IOPL_IOPERM
+ .invalidate_io_bitmap = xen_invalidate_io_bitmap,
.update_io_bitmap = xen_update_io_bitmap,
#endif
.io_delay = xen_io_delay,
--
2.25.1
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