[llvm-readobj] - Fix a crash when DT_STRTAB is broken.

We might have a crash scenario when we have an invalid DT_STRTAB value
that is larger than the file size. I've added a test case to demonstrate.

Differential revision: https://reviews.llvm.org/D76706

1 files changed, 12 insertions, 1 deletions

diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cpp
index f17a6da..d1bf469 100644
--- a/llvm/lib/Object/ELF.cpp
+++ b/llvm/lib/Object/ELF.cpp
@@ -580,7 +580,18 @@ Expected<const uint8_t *> ELFFile<ELFT>::toMappedAddr(uint64_t VAddr) const {
   if (Delta >= Phdr.p_filesz)
     return createError("virtual address is not in any segment: 0x" +
                        Twine::utohexstr(VAddr));
-  return base() + Phdr.p_offset + Delta;
+
+  uint64_t Offset = Phdr.p_offset + Delta;
+  if (Offset >= getBufSize())
+    return createError("can't map virtual address 0x" +
+                       Twine::utohexstr(VAddr) + " to the segment with index " +
+                       Twine(&Phdr - (*ProgramHeadersOrError).data() + 1) +
+                       ": the segment ends at 0x" +
+                       Twine::utohexstr(Phdr.p_offset + Phdr.p_filesz) +
+                       ", which is greater than the file size (0x" +
+                       Twine::utohexstr(getBufSize()) + ")");
+
+  return base() + Offset;
 }
 
 template class llvm::object::ELFFile<ELF32LE>;