[llvm] [Support] Check zstd decompress result before msan unpoison (PR #117276)

[Wu Yingcong via llvm-commits]

https://github.com/yingcong-wu created https://github.com/llvm/llvm-project/pull/117276

We should check the zstd decompress result before doing the msan unpoison. If the res is abnormal, then it would be a huge number, which will cause undesired msan unpoison behavior and will run for a long time.

>From eb4cb92c2c45b0e7ee352af962de1a1931e02d5b Mon Sep 17 00:00:00 2001
From: "Wu, Yingcong" <yingcong.wu at intel.com>
Date: Thu, 21 Nov 2024 18:28:53 -0800
Subject: [PATCH 1/2] check res before unpoison

---
 llvm/lib/Support/Compression.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Support/Compression.cpp b/llvm/lib/Support/Compression.cpp
index badaf68ab59cd0..6f3dd984416aa0 100644
--- a/llvm/lib/Support/Compression.cpp
+++ b/llvm/lib/Support/Compression.cpp
@@ -206,12 +206,14 @@ Error zstd::decompress(ArrayRef<uint8_t> Input, uint8_t *Output,
   const size_t Res = ::ZSTD_decompress(
       Output, UncompressedSize, (const uint8_t *)Input.data(), Input.size());
   UncompressedSize = Res;
+  if (ZSTD_isError(Res)) {
+    return make_error<StringError>(ZSTD_getErrorName(Res),
+                                   inconvertibleErrorCode());
+  }
   // Tell MemorySanitizer that zstd output buffer is fully initialized.
   // This avoids a false report when running LLVM with uninstrumented ZLib.
   __msan_unpoison(Output, UncompressedSize);
-  return ZSTD_isError(Res) ? make_error<StringError>(ZSTD_getErrorName(Res),
-                                                     inconvertibleErrorCode())
-                           : Error::success();
+  return Error::success();
 }
 
 Error zstd::decompress(ArrayRef<uint8_t> Input,

>From d710ec0b0c37b29d611fe63900b9ce42a8a9af4a Mon Sep 17 00:00:00 2001
From: "Wu, Yingcong" <yingcong.wu at intel.com>
Date: Thu, 21 Nov 2024 18:35:59 -0800
Subject: [PATCH 2/2] format

---
 llvm/lib/Support/Compression.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/llvm/lib/Support/Compression.cpp b/llvm/lib/Support/Compression.cpp
index 6f3dd984416aa0..3979ca6acaf74e 100644
--- a/llvm/lib/Support/Compression.cpp
+++ b/llvm/lib/Support/Compression.cpp
@@ -206,10 +206,9 @@ Error zstd::decompress(ArrayRef<uint8_t> Input, uint8_t *Output,
   const size_t Res = ::ZSTD_decompress(
       Output, UncompressedSize, (const uint8_t *)Input.data(), Input.size());
   UncompressedSize = Res;
-  if (ZSTD_isError(Res)) {
+  if (ZSTD_isError(Res))
     return make_error<StringError>(ZSTD_getErrorName(Res),
                                    inconvertibleErrorCode());
-  }
   // Tell MemorySanitizer that zstd output buffer is fully initialized.
   // This avoids a false report when running LLVM with uninstrumented ZLib.
   __msan_unpoison(Output, UncompressedSize);