[llvm] r339269 - [WASM] Fix overflow when reading custom section

[Jonas Devlieghere via llvm-commits]

Author: jdevlieghere
Date: Wed Aug  8 09:34:03 2018
New Revision: 339269

URL: http://llvm.org/viewvc/llvm-project?rev=339269&view=rev
Log:
[WASM] Fix overflow when reading custom section

When reading a custom WASM section, it was possible that its name
extended beyond the size of the section. This resulted in a bogus value
for the section size due to the size overflowing.

Fixes heap buffer overflow detected by OSS-fuzz:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=8190

Differential revision: https://reviews.llvm.org/D50387

Added:
    llvm/trunk/test/Object/Inputs/WASM/string-outside-section.wasm   (with props)
    llvm/trunk/test/Object/wasm-string-outside-section.test
Modified:
    llvm/trunk/lib/Object/WasmObjectFile.cpp

Modified: llvm/trunk/lib/Object/WasmObjectFile.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Object/WasmObjectFile.cpp?rev=339269&r1=339268&r2=339269&view=diff
==============================================================================
--- llvm/trunk/lib/Object/WasmObjectFile.cpp (original)
+++ llvm/trunk/lib/Object/WasmObjectFile.cpp Wed Aug  8 09:34:03 2018
@@ -216,9 +216,16 @@ static Error readSection(WasmSection &Se
     return make_error<StringError>("Section too large",
                                    object_error::parse_failed);
   if (Section.Type == wasm::WASM_SEC_CUSTOM) {
-    const uint8_t *NameStart = Ctx.Ptr;
-    Section.Name = readString(Ctx);
-    Size -= Ctx.Ptr - NameStart;
+    WasmObjectFile::ReadContext SectionCtx;
+    SectionCtx.Start = Ctx.Ptr;
+    SectionCtx.Ptr = Ctx.Ptr;
+    SectionCtx.End = Ctx.Ptr + Size;
+
+    Section.Name = readString(SectionCtx);
+
+    uint32_t SectionNameSize = SectionCtx.Ptr - SectionCtx.Start;
+    Ctx.Ptr += SectionNameSize;
+    Size -= SectionNameSize;
   }
   Section.Content = ArrayRef<uint8_t>(Ctx.Ptr, Size);
   Ctx.Ptr += Size;

Added: llvm/trunk/test/Object/Inputs/WASM/string-outside-section.wasm
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Object/Inputs/WASM/string-outside-section.wasm?rev=339269&view=auto
==============================================================================
Binary file - no diff available.

Propchange: llvm/trunk/test/Object/Inputs/WASM/string-outside-section.wasm
------------------------------------------------------------------------------
    svn:mime-type = application/octet-stream

Added: llvm/trunk/test/Object/wasm-string-outside-section.test
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Object/wasm-string-outside-section.test?rev=339269&view=auto
==============================================================================
--- llvm/trunk/test/Object/wasm-string-outside-section.test (added)
+++ llvm/trunk/test/Object/wasm-string-outside-section.test Wed Aug  8 09:34:03 2018
@@ -0,0 +1,3 @@
+RUN: not llvm-objdump -s %p/Inputs/WASM/string-outside-section.wasm 2>&1 | FileCheck %s
+
+CHECK: LLVM ERROR: EOF while reading string