[tip: x86/iopl] x86/ioperm: Extend IOPL config to control ioperm() as well

From: tip-bot2 for Thomas Gleixner
Date: Fri Nov 15 2019 - 16:13:33 EST

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID: 845fa6a960f45e07ab22b660bee7f7644dd29610
Gitweb: https://git.kernel.org/tip/845fa6a960f45e07ab22b660bee7f7644dd29610
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Wed, 13 Nov 2019 21:42:59 +01:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 14 Nov 2019 20:15:08 +01:00

x86/ioperm: Extend IOPL config to control ioperm() as well

If iopl() is disabled, then providing ioperm() does not make much sense.

Rename the config option and disable/enable both syscalls with it. Guard
the code with #ifdefs where appropriate.

Suggested-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20191113210105.557339819@xxxxxxxxxxxxx

---
arch/x86/Kconfig | 7 +++++--
arch/x86/include/asm/io_bitmap.h | 6 ++++++
arch/x86/include/asm/processor.h | 9 ++++++++-
arch/x86/include/asm/thread_info.h | 7 ++++++-
arch/x86/kernel/cpu/common.c | 26 +++++++++++++++++---------
arch/x86/kernel/ioport.c | 26 +++++++++++++++++++-------
arch/x86/kernel/process.c | 4 ++++
7 files changed, 65 insertions(+), 20 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1f926e3..b162ce1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1254,10 +1254,13 @@ config X86_VSYSCALL_EMULATION
Disabling this option saves about 7K of kernel size and
possibly 4K of additional runtime pagetable memory.

-config X86_IOPL_EMULATION
- bool "IOPL Emulation"
+config X86_IOPL_IOPERM
+ bool "IOPERM and IOPL Emulation"
default y
---help---
+ This enables the ioperm() and iopl() syscalls which are necessary
+ for legacy applications.
+
Legacy IOPL support is an overbroad mechanism which allows user
space aside of accessing all 65536 I/O ports also to disable
interrupts. To gain this access the caller needs CAP_SYS_RAWIO
diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index b664baa..02c6ef8 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -15,9 +15,15 @@ struct io_bitmap {

struct task_struct;

+#ifdef CONFIG_X86_IOPL_IOPERM
void io_bitmap_share(struct task_struct *tsk);
void io_bitmap_exit(void);

void tss_update_io_bitmap(void);
+#else
+static inline void io_bitmap_share(struct task_struct *tsk) { }
+static inline void io_bitmap_exit(void) { }
+static inline void tss_update_io_bitmap(void) { }
+#endif

#endif
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 1387d31..45f416a 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -340,13 +340,18 @@ struct x86_hw_tss {
(offsetof(struct tss_struct, io_bitmap.mapall) - \
offsetof(struct tss_struct, x86_tss))

+#ifdef CONFIG_X86_IOPL_IOPERM
/*
* sizeof(unsigned long) coming from an extra "long" at the end of the
* iobitmap. The limit is inclusive, i.e. the last valid byte.
*/
-#define __KERNEL_TSS_LIMIT \
+# define __KERNEL_TSS_LIMIT \
(IO_BITMAP_OFFSET_VALID_ALL + IO_BITMAP_BYTES + \
sizeof(unsigned long) - 1)
+#else
+# define __KERNEL_TSS_LIMIT \
+ (offsetof(struct tss_struct, x86_tss) + sizeof(struct x86_hw_tss) - 1)
+#endif

/* Base offset outside of TSS_LIMIT so unpriviledged IO causes #GP */
#define IO_BITMAP_OFFSET_INVALID (__KERNEL_TSS_LIMIT + 1)
@@ -398,7 +403,9 @@ struct tss_struct {
*/
struct x86_hw_tss x86_tss;

+#ifdef CONFIG_X86_IOPL_IOPERM
struct x86_io_bitmap io_bitmap;
+#endif
} __aligned(PAGE_SIZE);

DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 0accf44..d779366 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -156,8 +156,13 @@ struct thread_info {
# define _TIF_WORK_CTXSW (_TIF_WORK_CTXSW_BASE)
#endif

-#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
+#ifdef CONFIG_X86_IOPL_IOPERM
+# define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
_TIF_IO_BITMAP)
+#else
+# define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY)
+#endif
+
#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)

#define STACK_WARN (THREAD_SIZE/8)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 7bf402b..6f6ca6b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1804,6 +1804,22 @@ static inline void gdt_setup_doublefault_tss(int cpu)
}
#endif /* !CONFIG_X86_64 */

+static inline void tss_setup_io_bitmap(struct tss_struct *tss)
+{
+ tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+
+#ifdef CONFIG_X86_IOPL_IOPERM
+ tss->io_bitmap.prev_max = 0;
+ tss->io_bitmap.prev_sequence = 0;
+ memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
+ /*
+ * Invalidate the extra array entry past the end of the all
+ * permission bitmap as required by the hardware.
+ */
+ tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL;
+#endif
+}
+
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
@@ -1860,15 +1876,7 @@ void cpu_init(void)

/* Initialize the TSS. */
tss_setup_ist(tss);
- tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
- tss->io_bitmap.prev_max = 0;
- tss->io_bitmap.prev_sequence = 0;
- memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
- /*
- * Invalidate the extra array entry past the end of the all
- * permission bitmap as required by the hardware.
- */
- tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL;
+ tss_setup_io_bitmap(tss);
set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);

load_TR_desc();
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index d5dcde9..8abeee0 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -14,6 +14,8 @@
#include <asm/io_bitmap.h>
#include <asm/desc.h>

+#ifdef CONFIG_X86_IOPL_IOPERM
+
static atomic64_t io_bitmap_sequence;

void io_bitmap_share(struct task_struct *tsk)
@@ -172,13 +174,6 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
struct thread_struct *t = &current->thread;
unsigned int old;

- /*
- * Careful: the IOPL bits in regs->flags are undefined under Xen PV
- * and changing them has no effect.
- */
- if (IS_ENABLED(CONFIG_X86_IOPL_NONE))
- return -ENOSYS;
-
if (level > 3)
return -EINVAL;

@@ -200,3 +195,20 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)

return 0;
}
+
+#else /* CONFIG_X86_IOPL_IOPERM */
+
+long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
+{
+ return -ENOSYS;
+}
+SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
+{
+ return -ENOSYS;
+}
+
+SYSCALL_DEFINE1(iopl, unsigned int, level)
+{
+ return -ENOSYS;
+}
+#endif
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 8ba2707..77a7d8f 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -316,6 +316,7 @@ void arch_setup_new_exec(void)
}
}

+#ifdef CONFIG_X86_IOPL_IOPERM
static inline void tss_invalidate_io_bitmap(struct tss_struct *tss)
{
/*
@@ -403,6 +404,9 @@ void tss_update_io_bitmap(void)
tss_invalidate_io_bitmap(tss);
}
}
+#else /* CONFIG_X86_IOPL_IOPERM */
+static inline void switch_to_bitmap(unsigned long tifp) { }
+#endif

#ifdef CONFIG_SMP