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, 37 insertions, 0 deletions

diff --git a/drivers/video/fbdev/atafb.h b/drivers/video/fbdev/atafb.h
new file mode 100644
index 000000000..2b2675980
--- /dev/null
+++ b/drivers/video/fbdev/atafb.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _VIDEO_ATAFB_H
+#define _VIDEO_ATAFB_H
+
+void atafb_mfb_copyarea(struct fb_info *info, u_long next_line, int sy, int sx, int dy,
+			int dx, int height, int width);
+void atafb_mfb_fillrect(struct fb_info *info, u_long next_line, u32 color,
+			int sy, int sx, int height, int width);
+void atafb_mfb_linefill(struct fb_info *info, u_long next_line,
+			int dy, int dx, u32 width,
+			const u8 *data, u32 bgcolor, u32 fgcolor);
+
+void atafb_iplan2p2_copyarea(struct fb_info *info, u_long next_line, int sy, int sx, int dy,
+			     int dx, int height, int width);
+void atafb_iplan2p2_fillrect(struct fb_info *info, u_long next_line, u32 color,
+			     int sy, int sx, int height, int width);
+void atafb_iplan2p2_linefill(struct fb_info *info, u_long next_line,
+			     int dy, int dx, u32 width,
+			     const u8 *data, u32 bgcolor, u32 fgcolor);
+
+void atafb_iplan2p4_copyarea(struct fb_info *info, u_long next_line, int sy, int sx, int dy,
+			     int dx, int height, int width);
+void atafb_iplan2p4_fillrect(struct fb_info *info, u_long next_line, u32 color,
+			     int sy, int sx, int height, int width);
+void atafb_iplan2p4_linefill(struct fb_info *info, u_long next_line,
+			     int dy, int dx, u32 width,
+			     const u8 *data, u32 bgcolor, u32 fgcolor);
+
+void atafb_iplan2p8_copyarea(struct fb_info *info, u_long next_line, int sy, int sx, int dy,
+			     int dx, int height, int width);
+void atafb_iplan2p8_fillrect(struct fb_info *info, u_long next_line, u32 color,
+			     int sy, int sx, int height, int width);
+void atafb_iplan2p8_linefill(struct fb_info *info, u_long next_line,
+			     int dy, int dx, u32 width,
+			     const u8 *data, u32 bgcolor, u32 fgcolor);
+
+#endif /* _VIDEO_ATAFB_H */