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Subject[PATCH 3/7] x86/vm86: Move userspace accesses to do_sys_vm86()
Date
Move the userspace accesses down into the common function in preparation for
the next set of patches. Also change to copying the fields explicitly instead
of assuming a fixed order in pt_regs and the kernel data structures.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
arch/x86/include/asm/processor.h | 2 +-
arch/x86/kernel/vm86_32.c | 189 +++++++++++++++++++++------------------
2 files changed, 102 insertions(+), 89 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index f4e4e3f..35ad554 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -405,7 +405,7 @@ struct thread_struct {
unsigned long error_code;
#ifdef CONFIG_X86_32
/* Virtual 86 mode info */
- struct vm86_struct __user *vm86_info;
+ struct vm86plus_struct __user *vm86_info;
unsigned long screen_bitmap;
unsigned long v86flags;
unsigned long v86mask;
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 9a2dc80..e6c2b47 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -90,46 +90,13 @@
#define SAFE_MASK (0xDD5)
#define RETURN_MASK (0xDFF)

-/* convert kernel_vm86_regs to vm86_regs */
-static int copy_vm86_regs_to_user(struct vm86_regs __user *user,
- const struct kernel_vm86_regs *regs)
-{
- int ret = 0;
-
- /*
- * kernel_vm86_regs is missing gs, so copy everything up to
- * (but not including) orig_eax, and then rest including orig_eax.
- */
- ret += copy_to_user(user, regs, offsetof(struct kernel_vm86_regs, pt.orig_ax));
- ret += copy_to_user(&user->orig_eax, &regs->pt.orig_ax,
- sizeof(struct kernel_vm86_regs) -
- offsetof(struct kernel_vm86_regs, pt.orig_ax));
-
- return ret;
-}
-
-/* convert vm86_regs to kernel_vm86_regs */
-static int copy_vm86_regs_from_user(struct kernel_vm86_regs *regs,
- const struct vm86_regs __user *user,
- unsigned extra)
-{
- int ret = 0;
-
- /* copy ax-fs inclusive */
- ret += copy_from_user(regs, user, offsetof(struct kernel_vm86_regs, pt.orig_ax));
- /* copy orig_ax-__gsh+extra */
- ret += copy_from_user(&regs->pt.orig_ax, &user->orig_eax,
- sizeof(struct kernel_vm86_regs) -
- offsetof(struct kernel_vm86_regs, pt.orig_ax) +
- extra);
- return ret;
-}
-
struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
{
struct tss_struct *tss;
struct pt_regs *ret;
- unsigned long tmp;
+ struct task_struct *tsk = current;
+ struct vm86plus_struct __user *user;
+ long err = 0;

/*
* This gets called from entry.S with interrupts disabled, but
@@ -138,23 +105,50 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
*/
local_irq_enable();

- if (!current->thread.vm86_info) {
+ if (!tsk->thread.vm86_info) {
pr_alert("no vm86_info: BAD\n");
do_exit(SIGSEGV);
}
- set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | current->thread.v86mask);
- tmp = copy_vm86_regs_to_user(&current->thread.vm86_info->regs, regs);
- tmp += put_user(current->thread.screen_bitmap, &current->thread.vm86_info->screen_bitmap);
- if (tmp) {
+ set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | tsk->thread.v86mask);
+ user = tsk->thread.vm86_info;
+
+ if (!access_ok(VERIFY_WRITE, user, VMPI.is_vm86pus ?
+ sizeof(struct vm86plus_struct) :
+ sizeof(struct vm86_struct))) {
+ pr_alert("could not access userspace vm86_info\n");
+ do_exit(SIGSEGV);
+ }
+
+ put_user_try {
+ put_user_ex(regs->pt.bx, &user->regs.ebx);
+ put_user_ex(regs->pt.cx, &user->regs.ecx);
+ put_user_ex(regs->pt.dx, &user->regs.edx);
+ put_user_ex(regs->pt.si, &user->regs.esi);
+ put_user_ex(regs->pt.di, &user->regs.edi);
+ put_user_ex(regs->pt.bp, &user->regs.ebp);
+ put_user_ex(regs->pt.ax, &user->regs.eax);
+ put_user_ex(regs->pt.ip, &user->regs.eip);
+ put_user_ex(regs->pt.cs, &user->regs.cs);
+ put_user_ex(regs->pt.flags, &user->regs.eflags);
+ put_user_ex(regs->pt.sp, &user->regs.esp);
+ put_user_ex(regs->pt.ss, &user->regs.ss);
+ put_user_ex(regs->es, &user->regs.es);
+ put_user_ex(regs->ds, &user->regs.ds);
+ put_user_ex(regs->fs, &user->regs.fs);
+ put_user_ex(regs->gs, &user->regs.gs);
+
+ put_user_ex(tsk->thread.screen_bitmap, &user->screen_bitmap);
+ } put_user_catch(err);
+ if (err) {
pr_alert("could not access userspace vm86_info\n");
do_exit(SIGSEGV);
}

tss = &per_cpu(cpu_tss, get_cpu());
- current->thread.sp0 = current->thread.saved_sp0;
- current->thread.sysenter_cs = __KERNEL_CS;
- load_sp0(tss, &current->thread);
- current->thread.saved_sp0 = 0;
+ tsk->thread.sp0 = tsk->thread.saved_sp0;
+ tsk->thread.sysenter_cs = __KERNEL_CS;
+ load_sp0(tss, &tsk->thread);
+ tsk->thread.saved_sp0 = 0;
put_cpu();

ret = KVM86->regs32;
@@ -199,7 +193,8 @@ out:


static int do_vm86_irq_handling(int subfunction, int irqnumber);
-static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk);
+static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
+ struct kernel_vm86_struct *info);

SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, v86)
{
@@ -208,21 +203,8 @@ SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, v86)
* This remains on the stack until we
* return to 32 bit user space.
*/
- struct task_struct *tsk = current;
- int tmp;

- if (tsk->thread.saved_sp0)
- return -EPERM;
- tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
- offsetof(struct kernel_vm86_struct, vm86plus) -
- sizeof(info.regs));
- if (tmp)
- return -EFAULT;
- memset(&info.vm86plus, 0, (int)&info.regs32 - (int)&info.vm86plus);
- info.regs32 = current_pt_regs();
- tsk->thread.vm86_info = v86;
- do_sys_vm86(&info, tsk);
- return 0; /* we never return here */
+ return do_sys_vm86((struct vm86plus_struct __user *) v86, false, &info);
}


@@ -233,11 +215,7 @@ SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
* This remains on the stack until we
* return to 32 bit user space.
*/
- struct task_struct *tsk;
- int tmp;
- struct vm86plus_struct __user *v86;

- tsk = current;
switch (cmd) {
case VM86_REQUEST_IRQ:
case VM86_FREE_IRQ:
@@ -255,34 +233,69 @@ SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
}

/* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
- if (tsk->thread.saved_sp0)
- return -EPERM;
- v86 = (struct vm86plus_struct __user *)arg;
- tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
- offsetof(struct kernel_vm86_struct, regs32) -
- sizeof(info.regs));
- if (tmp)
- return -EFAULT;
- info.regs32 = current_pt_regs();
- info.vm86plus.is_vm86pus = 1;
- tsk->thread.vm86_info = (struct vm86_struct __user *)v86;
- do_sys_vm86(&info, tsk);
- return 0; /* we never return here */
+ return do_sys_vm86((struct vm86plus_struct __user *) arg, true, &info);
}


-static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk)
+static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
+ struct kernel_vm86_struct *info)
{
struct tss_struct *tss;
-/*
- * make sure the vm86() system call doesn't try to do anything silly
- */
- info->regs.pt.ds = 0;
- info->regs.pt.es = 0;
- info->regs.pt.fs = 0;
-#ifndef CONFIG_X86_32_LAZY_GS
- info->regs.pt.gs = 0;
-#endif
+ struct task_struct *tsk = current;
+ unsigned long err = 0;
+
+ if (tsk->thread.saved_sp0)
+ return -EPERM;
+
+ if (!access_ok(VERIFY_READ, v86, plus ?
+ sizeof(struct vm86_struct) :
+ sizeof(struct vm86plus_struct)))
+ return -EFAULT;
+
+ memset(info, 0, sizeof(*info));
+ get_user_try {
+ unsigned short seg;
+ get_user_ex(info->regs.pt.bx, &v86->regs.ebx);
+ get_user_ex(info->regs.pt.cx, &v86->regs.ecx);
+ get_user_ex(info->regs.pt.dx, &v86->regs.edx);
+ get_user_ex(info->regs.pt.si, &v86->regs.esi);
+ get_user_ex(info->regs.pt.di, &v86->regs.edi);
+ get_user_ex(info->regs.pt.bp, &v86->regs.ebp);
+ get_user_ex(info->regs.pt.ax, &v86->regs.eax);
+ get_user_ex(info->regs.pt.ip, &v86->regs.eip);
+ get_user_ex(seg, &v86->regs.cs);
+ info->regs.pt.cs = seg;
+ get_user_ex(info->regs.pt.flags, &v86->regs.eflags);
+ get_user_ex(info->regs.pt.sp, &v86->regs.esp);
+ get_user_ex(seg, &v86->regs.ss);
+ info->regs.pt.ss = seg;
+ get_user_ex(info->regs.es, &v86->regs.es);
+ get_user_ex(info->regs.ds, &v86->regs.ds);
+ get_user_ex(info->regs.fs, &v86->regs.fs);
+ get_user_ex(info->regs.gs, &v86->regs.gs);
+
+ get_user_ex(info->flags, &v86->flags);
+ get_user_ex(info->screen_bitmap, &v86->screen_bitmap);
+ get_user_ex(info->cpu_type, &v86->cpu_type);
+ } get_user_catch(err);
+ if (err)
+ return err;
+
+ if (copy_from_user(&info->int_revectored, &v86->int_revectored,
+ sizeof(struct revectored_struct)))
+ return -EFAULT;
+ if (copy_from_user(&info->int21_revectored, &v86->int21_revectored,
+ sizeof(struct revectored_struct)))
+ return -EFAULT;
+ if (plus) {
+ if (copy_from_user(&info->vm86plus, &v86->vm86plus,
+ sizeof(struct vm86plus_info_struct)))
+ return -EFAULT;
+ info->vm86plus.is_vm86pus = 1;
+ }
+
+ info->regs32 = current_pt_regs();
+ tsk->thread.vm86_info = v86;

/*
* The flags register is also special: we cannot trust that the user
@@ -344,7 +357,7 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
"jmp resume_userspace"
: /* no outputs */
:"r" (&info->regs), "r" (task_thread_info(tsk)), "r" (0));
- /* we never return here */
+ unreachable(); /* we never return here */
}

static inline void return_to_32bit(struct kernel_vm86_regs *regs16, int retval)
--
2.4.3


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