fix compat console unimap regression

Why is it that since the 2f1a2ccb9c0de632ab07193becf5f7121794f6ae console
UTF-8 fixes went into 2.6.22-rc1, the PowerMac G5 shows only inverse video
question marks for the text on tty2-6? whereas tty1 is fine, and so is x86.

No fault of that patch: by removing the old fallback behaviour, it reveals
that 32-bit setfont running on 64-bit kernels has only really worked on
the current console, the rest getting faked by that inadequate fallback.

Bring the compat do_unimap_ioctl into line with the main one: PIO_UNIMAP
and GIO_UNIMAP apply to the specified tty, not redirected to fg_console.
Use the same checks, and most particularly, remember to check access_ok:
con_set_unimap and con_get_unimap are using __get_user and __put_user.

And the compat vt_check should ask for the same capability as the main
one, CAP_SYS_TTY_CONFIG rather than CAP_SYS_ADMIN.  Added in vt_ioctl's
vc_cons_allocated check for safety, though failure may well be impossible.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 8 deletions

diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index 65643def3182..6b44cdc96fac 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -1194,6 +1194,7 @@ static int vt_check(struct file *file)
 {
         struct tty_struct *tty;
         struct inode *inode = file->f_path.dentry->d_inode;
+        struct vc_data *vc;
         
         if (file->f_op->ioctl != tty_ioctl)
                 return -EINVAL;
@@ -1204,12 +1205,16 @@ static int vt_check(struct file *file)
                                                         
         if (tty->driver->ioctl != vt_ioctl)
                 return -EINVAL;
-        
+
+        vc = (struct vc_data *)tty->driver_data;
+        if (!vc_cons_allocated(vc->vc_num))     /* impossible? */
+                return -ENOIOCTLCMD;
+
         /*
          * To have permissions to do most of the vt ioctls, we either have
-         * to be the owner of the tty, or super-user.
+         * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
          */
-        if (current->signal->tty == tty || capable(CAP_SYS_ADMIN))
+        if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
                 return 1;
         return 0;                                                    
 }
@@ -1310,16 +1315,28 @@ static int do_unimap_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg,
         struct unimapdesc32 tmp;
         struct unimapdesc32 __user *user_ud = compat_ptr(arg);
         int perm = vt_check(file);
-        
-        if (perm < 0) return perm;
+        struct vc_data *vc;
+
+        if (perm < 0)
+                return perm;
         if (copy_from_user(&tmp, user_ud, sizeof tmp))
                 return -EFAULT;
+        if (tmp.entries)
+                if (!access_ok(VERIFY_WRITE, compat_ptr(tmp.entries),
+                                tmp.entry_ct*sizeof(struct unipair)))
+                        return -EFAULT;
+        vc = ((struct tty_struct *)file->private_data)->driver_data;
         switch (cmd) {
         case PIO_UNIMAP:
-                if (!perm) return -EPERM;
-                return con_set_unimap(vc_cons[fg_console].d, tmp.entry_ct, compat_ptr(tmp.entries));
+                if (!perm)
+                        return -EPERM;
+                return con_set_unimap(vc, tmp.entry_ct,
+                                                compat_ptr(tmp.entries));
         case GIO_UNIMAP:
-                return con_get_unimap(vc_cons[fg_console].d, tmp.entry_ct, &(user_ud->entry_ct), compat_ptr(tmp.entries));
+                if (!perm && fg_console != vc->vc_num)
+                        return -EPERM;
+                return con_get_unimap(vc, tmp.entry_ct, &(user_ud->entry_ct),
+                                                compat_ptr(tmp.entries));
         }
         return 0;
 }