vm86: get rid of get_user_ex() use

Just do a copyin of what we want into a local variable and
be done with that.  We are guaranteed to be on shallow stack
here...

Note that conditional expression for range passed to access_ok()
in mainline had been pointless all along - the only difference
between vm86plus_struct and vm86_struct is that the former has
one extra field in the end and when we get to copyin of that
field (conditional upon 'plus' argument), we use copy_from_user().
Moreover, all fields starting with ->int_revectored are copied
that way, so we only need that check (be it done by access_ok()
or by user_access_begin()) only on the beginning of the structure -
the fields that used to be covered by that get_user_try() block.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 91d55454e7022aa7b93a1a1da1202cded5dc3e99..49b37eb01e9937766ee218410720bf9b65e20cdb 100644 (file)
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -243,6 +243,7 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
        struct kernel_vm86_regs vm86regs;
        struct pt_regs *regs = current_pt_regs();
        unsigned long err = 0;
+       struct vm86_struct v;
 
        err = security_mmap_addr(0);
        if (err) {
@@ -278,39 +279,32 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
        if (vm86->saved_sp0)
                return -EPERM;
 
-       if (!access_ok(user_vm86, plus ?
-                      sizeof(struct vm86_struct) :
-                      sizeof(struct vm86plus_struct)))
+       if (copy_from_user(&v, user_vm86,
+                       offsetof(struct vm86_struct, int_revectored)))
                return -EFAULT;
 
        memset(&vm86regs, 0, sizeof(vm86regs));
-       get_user_try {
-               unsigned short seg;
-               get_user_ex(vm86regs.pt.bx, &user_vm86->regs.ebx);
-               get_user_ex(vm86regs.pt.cx, &user_vm86->regs.ecx);
-               get_user_ex(vm86regs.pt.dx, &user_vm86->regs.edx);
-               get_user_ex(vm86regs.pt.si, &user_vm86->regs.esi);
-               get_user_ex(vm86regs.pt.di, &user_vm86->regs.edi);
-               get_user_ex(vm86regs.pt.bp, &user_vm86->regs.ebp);
-               get_user_ex(vm86regs.pt.ax, &user_vm86->regs.eax);
-               get_user_ex(vm86regs.pt.ip, &user_vm86->regs.eip);
-               get_user_ex(seg, &user_vm86->regs.cs);
-               vm86regs.pt.cs = seg;
-               get_user_ex(vm86regs.pt.flags, &user_vm86->regs.eflags);
-               get_user_ex(vm86regs.pt.sp, &user_vm86->regs.esp);
-               get_user_ex(seg, &user_vm86->regs.ss);
-               vm86regs.pt.ss = seg;
-               get_user_ex(vm86regs.es, &user_vm86->regs.es);
-               get_user_ex(vm86regs.ds, &user_vm86->regs.ds);
-               get_user_ex(vm86regs.fs, &user_vm86->regs.fs);
-               get_user_ex(vm86regs.gs, &user_vm86->regs.gs);
-
-               get_user_ex(vm86->flags, &user_vm86->flags);
-               get_user_ex(vm86->screen_bitmap, &user_vm86->screen_bitmap);
-               get_user_ex(vm86->cpu_type, &user_vm86->cpu_type);
-       } get_user_catch(err);
-       if (err)
-               return err;
+
+       vm86regs.pt.bx = v.regs.ebx;
+       vm86regs.pt.cx = v.regs.ecx;
+       vm86regs.pt.dx = v.regs.edx;
+       vm86regs.pt.si = v.regs.esi;
+       vm86regs.pt.di = v.regs.edi;
+       vm86regs.pt.bp = v.regs.ebp;
+       vm86regs.pt.ax = v.regs.eax;
+       vm86regs.pt.ip = v.regs.eip;
+       vm86regs.pt.cs = v.regs.cs;
+       vm86regs.pt.flags = v.regs.eflags;
+       vm86regs.pt.sp = v.regs.esp;
+       vm86regs.pt.ss = v.regs.ss;
+       vm86regs.es = v.regs.es;
+       vm86regs.ds = v.regs.ds;
+       vm86regs.fs = v.regs.fs;
+       vm86regs.gs = v.regs.gs;
+
+       vm86->flags = v.flags;
+       vm86->screen_bitmap = v.screen_bitmap;
+       vm86->cpu_type = v.cpu_type;
 
        if (copy_from_user(&vm86->int_revectored,
                           &user_vm86->int_revectored,