fix TOCTOU in command pager

Phillip Davis created 6 months ago

- in CommandSession constructor, must construct a hard reference to the
  ViewPager to make garbage collection impossible until at least
  `getContext()` is called
- in setupLayoutManager, current code doesn't have a case for if mPager
  is null. Probably we wouldn't be there anyway, but in any case the
  `ctx` parameter should be equivalent, i.e., it should refer to the
  ActivityContext, so we use that instead of going through mPager

Change summary

src/main/java/eu/siacs/conversations/entities/Conversation.java | 5 +-
1 file changed, 3 insertions(+), 2 deletions(-)

Detailed changes

src/main/java/eu/siacs/conversations/entities/Conversation.java

@@ -3144,7 +3144,8 @@ public class Conversation extends AbstractEntity
                 mTitle = title;
                 mNode = node;
                 this.xmppConnectionService = xmppConnectionService;
-                if (mPager.get() != null) setupLayoutManager(mPager.get().getContext());
+                ViewPager pager = mPager.get();
+                if (pager != null) setupLayoutManager(pager.getContext());
             }
 
             public String getTitle() {
@@ -3652,7 +3653,7 @@ public class Conversation extends AbstractEntity
 
                 if (reported != null) {
                     float screenWidth = ctx.getResources().getDisplayMetrics().widthPixels;
-                    TextPaint paint = ((TextView) LayoutInflater.from(mPager.get().getContext()).inflate(R.layout.command_result_cell, null)).getPaint();
+                    TextPaint paint = ((TextView) LayoutInflater.from(ctx).inflate(R.layout.command_result_cell, null)).getPaint();
                     float tableHeaderWidth = reported.stream().reduce(
                         0f,
                         (total, field) -> total + StaticLayout.getDesiredWidth(field.getLabel().or("--------") + "\t", paint),