[patch 20/54] fix compat console unimap regression

From: Chris Wright
Date: Fri Jun 08 2007 - 03:39:14 EST

-stable review patch. If anyone has any objections, please let us know.

From: Hugh Dickins <hugh@xxxxxxxxxxx>

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@xxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

fs/compat_ioctl.c | 33 +++++++++++++++++++++++++--------
1 file changed, 25 insertions(+), 8 deletions(-)

--- linux-
+++ linux-
@@ -1178,6 +1178,7 @@ 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;
@@ -1188,12 +1189,16 @@ 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;
@@ -1294,16 +1299,28 @@ static int do_unimap_ioctl(unsigned int
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) {
- 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));
- 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;

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