[PATCH] fbdev: fix kernel panic from FBIO_CURSOR ioctl

1. This fixes a kernel oops when issuing an FBIO_CURSOR ioctl if struct
   fb_cursor_user is filled with zero/NULLs.  Reported by Yuval Kogman
   <nothingmuch@woobling.org>.

2. This also fixes the cursor corruption in soft_cursor when
   sprite.scan_align != 1.
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/video/fbmem.c

@@ -974,7 +974,7 @@ fb_cursor(struct fb_info *info, struct fb_cursor_user __user *sprite)
 {
 	struct fb_cursor_user cursor_user;
 	struct fb_cursor cursor;
-	char *data = NULL, *mask = NULL;
+	char *data = NULL, *mask = NULL, *info_mask = NULL;
 	u16 *red = NULL, *green = NULL, *blue = NULL, *transp = NULL;
 	int err = -EINVAL;
 	
@@ -982,12 +982,12 @@ fb_cursor(struct fb_info *info, struct fb_cursor_user __user *sprite)
 		return -EFAULT;
 
 	memcpy(&cursor, &cursor_user, sizeof(cursor_user));
-	cursor.mask = NULL;
-	cursor.image.data = NULL;
-	cursor.image.cmap.red = NULL;
-	cursor.image.cmap.green = NULL;
-	cursor.image.cmap.blue = NULL;
-	cursor.image.cmap.transp = NULL;
+	cursor.mask = info->cursor.mask;
+	cursor.image.data = info->cursor.image.data;
+	cursor.image.cmap.red = info->cursor.image.cmap.red;
+	cursor.image.cmap.green = info->cursor.image.cmap.green;
+	cursor.image.cmap.blue = info->cursor.image.cmap.blue;
+	cursor.image.cmap.transp = info->cursor.image.cmap.transp;
 	cursor.data = NULL;
 
 	if (cursor.set & FB_CUR_SETCUR)
@@ -1047,6 +1047,8 @@ fb_cursor(struct fb_info *info, struct fb_cursor_user __user *sprite)
 		
 		cursor.image.data = data;
 		cursor.mask = mask;
+		info_mask = (char *) info->cursor.mask;
+		info->cursor.mask = mask;
 	}
 	info->cursor.set = cursor.set;
 	info->cursor.rop = cursor.rop;
@@ -1058,6 +1060,8 @@ fb_cursor(struct fb_info *info, struct fb_cursor_user __user *sprite)
 	kfree(green);
 	kfree(blue);
 	kfree(transp);
+	if (info_mask)
+		info->cursor.mask = info_mask;
 	return err;
 }
 

drivers/video/softcursor.c

@@ -22,7 +22,8 @@ int soft_cursor(struct fb_info *info, struct fb_cursor *cursor)
 	unsigned int scan_align = info->sprite.scan_align - 1;
 	unsigned int buf_align = info->sprite.buf_align - 1;
 	unsigned int i, size, dsize, s_pitch, d_pitch;
-	u8 *dst, src[64];
+	struct fb_cursor *cur;
+	u8 *dst, *src;
 
 	if (cursor->set & FB_CUR_SETSIZE) {
 		info->cursor.image.height = cursor->image.height;
@@ -48,9 +49,17 @@ int soft_cursor(struct fb_info *info, struct fb_cursor *cursor)
 		info->cursor.image.depth = cursor->image.depth;
 	}	
 
+	info->cursor.image.data = cursor->image.data;
+
 	if (info->state != FBINFO_STATE_RUNNING)
 		return 0;
 
+	src = kmalloc(64 + sizeof(struct fb_cursor), GFP_ATOMIC);
+	if (!src)
+		return -ENOMEM;
+	cur = (struct fb_cursor *) (src + 64);
+	*cur = info->cursor;
+
 	s_pitch = (info->cursor.image.width + 7) >> 3;
 	dsize = s_pitch * info->cursor.image.height;
 	d_pitch = (s_pitch + scan_align) & ~scan_align;
@@ -79,9 +88,12 @@ int soft_cursor(struct fb_info *info, struct fb_cursor *cursor)
 	else
 		fb_sysmove_buf_aligned(info, &info->sprite, dst, d_pitch, src,
 				   s_pitch, info->cursor.image.height);
-	info->cursor.image.data = dst;
+	cur->image.data = dst;
 	
-	info->fbops->fb_imageblit(info, &info->cursor.image);
+	info->fbops->fb_imageblit(info, &cur->image);
+
+	kfree(src);
+
 	return 0;
 }