fix(cfi): Skip u64::MAX FDEs when converting DWARF (#868)

We have seen FDEs with an initial address of u64::MAX in user-provided DWARF files. Such FDEs will invariably fail to process because of either an address overflow error in gimli or an underflow in the length calculation in line 756. Therefore, we skip them immediately so we don't abort the processing of the entire file.

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+**Fixes**
+- symbolic-cfi: Skip invalid FDEs when converting DWARF to Breakpad CFI ([#868](https://github.com/getsentry/symbolic/pull/868))
+
 **Internal**:
 
 - Removed `dmsort` dependency and replaced uses with stable std sorts. ([#869](https://github.com/getsentry/symbolic/pull/869))

symbolic-cfi/src/lib.rs

@@ -717,6 +717,15 @@ impl<W: Write> AsciiCfiWriter<W> {
         R: Reader + Eq,
         U: UnwindSection<R>,
     {
+        // We have seen FDEs with an initial address of `u64::MAX` in user-provided
+        // DWARF files. Such FDEs will invariably fail to process because of either
+        // an address overflow error in `gimli` or an underflow in the `length`
+        // calculation below. Therefore, we skip them immediately so we don't abort
+        // the processing of the entire file.
+        if fde.initial_address() == u64::MAX {
+            return Ok(());
+        }
+
         // Retrieves the register that specifies the return address. We need to assign a special
         // format to this register for Breakpad.
         let ra = fde.cie().return_address_register();