openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 78 insertions, 0 deletions

diff --git a/Documentation/fb/tridentfb.rst b/Documentation/fb/tridentfb.rst
new file mode 100644
index 000000000..7921c9dee
--- /dev/null
+++ b/Documentation/fb/tridentfb.rst
@@ -0,0 +1,78 @@
+=========
+Tridentfb
+=========
+
+Tridentfb is a framebuffer driver for some Trident chip based cards.
+
+The following list of chips is thought to be supported although not all are
+tested:
+
+those from the TGUI series 9440/96XX and with Cyber in their names
+those from the Image series and with Cyber in their names
+those with Blade in their names (Blade3D,CyberBlade...)
+the newer CyberBladeXP family
+
+All families are accelerated. Only PCI/AGP based cards are supported,
+none of the older Tridents.
+The driver supports 8, 16 and 32 bits per pixel depths.
+The TGUI family requires a line length to be power of 2 if acceleration
+is enabled. This means that range of possible resolutions and bpp is
+limited comparing to the range if acceleration is disabled (see list
+of parameters below).
+
+Known bugs:
+
+1. The driver randomly locks up on 3DImage975 chip with acceleration
+   enabled. The same happens in X11 (Xorg).
+2. The ramdac speeds require some more fine tuning. It is possible to
+   switch resolution which the chip does not support at some depths for
+   older chips.
+
+How to use it?
+==============
+
+When booting you can pass the video parameter::
+
+	video=tridentfb
+
+The parameters for tridentfb are concatenated with a ':' as in this example::
+
+	video=tridentfb:800x600-16@75,noaccel
+
+The second level parameters that tridentfb understands are:
+
+========  =====================================================================
+noaccel   turns off acceleration (when it doesn't work for your card)
+
+fp	  use flat panel related stuff
+crt 	  assume monitor is present instead of fp
+
+center 	  for flat panels and resolutions smaller than native size center the
+	  image, otherwise use
+stretch
+
+memsize   integer value in KB, use if your card's memory size is misdetected.
+	  look at the driver output to see what it says when initializing.
+
+memdiff   integer value in KB, should be nonzero if your card reports
+	  more memory than it actually has. For instance mine is 192K less than
+	  detection says in all three BIOS selectable situations 2M, 4M, 8M.
+	  Only use if your video memory is taken from main memory hence of
+	  configurable size. Otherwise use memsize.
+	  If in some modes which barely fit the memory you see garbage
+	  at the bottom this might help by not letting change to that mode
+	  anymore.
+
+nativex   the width in pixels of the flat panel.If you know it (usually 1024
+	  800 or 1280) and it is not what the driver seems to detect use it.
+
+bpp	  bits per pixel (8,16 or 32)
+mode	  a mode name like 800x600-8@75 as described in
+	  Documentation/fb/modedb.rst
+========  =====================================================================
+
+Using insane values for the above parameters will probably result in driver
+misbehaviour so take care(for instance memsize=12345678 or memdiff=23784 or
+nativex=93)
+
+Contact: jani@astechnix.ro