[llvm-branch-commits] [compiler-rt] release/19.x: Reapply "[sanitizer_common] AND signals in BlockSignals instead of deleting (#113443)" for non-Android Linux only (#115790) (PR #116670)

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: None (llvmbot)

<details>
<summary>Changes</summary>

Backport 531acf9e2f24977d2556b39229b22f4518a1faa5

Requested by: @<!-- -->thurstond

---
Full diff: https://github.com/llvm/llvm-project/pull/116670.diff


3 Files Affected:

- (modified) compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp (+39-16) 
- (modified) compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt (+1) 
- (added) compiler-rt/lib/sanitizer_common/tests/sanitizer_block_signals.cpp (+76) 


``````````diff
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
index b9b1f496df7c98..be3b3bd94e2a58 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
@@ -160,33 +160,56 @@ void SetSigProcMask(__sanitizer_sigset_t *set, __sanitizer_sigset_t *oldset) {
   CHECK_EQ(0, internal_sigprocmask(SIG_SETMASK, set, oldset));
 }
 
+#  if SANITIZER_LINUX
+// Deletes the specified signal from newset, if it is not present in oldset
+// Equivalently: newset[signum] = newset[signum] & oldset[signum]
+static void KeepUnblocked(__sanitizer_sigset_t &newset,
+                          __sanitizer_sigset_t &oldset, int signum) {
+  // FIXME: https://github.com/google/sanitizers/issues/1816
+  if (SANITIZER_ANDROID || !internal_sigismember(&oldset, signum))
+    internal_sigdelset(&newset, signum);
+}
+#  endif
+
 // Block asynchronous signals
 void BlockSignals(__sanitizer_sigset_t *oldset) {
-  __sanitizer_sigset_t set;
-  internal_sigfillset(&set);
-#  if SANITIZER_LINUX && !SANITIZER_ANDROID
+  __sanitizer_sigset_t newset;
+  internal_sigfillset(&newset);
+
+#  if SANITIZER_LINUX
+  __sanitizer_sigset_t currentset;
+
+#    if !SANITIZER_ANDROID
+  // FIXME: https://github.com/google/sanitizers/issues/1816
+  SetSigProcMask(NULL, &currentset);
+
   // Glibc uses SIGSETXID signal during setuid call. If this signal is blocked
   // on any thread, setuid call hangs.
   // See test/sanitizer_common/TestCases/Linux/setuid.c.
-  internal_sigdelset(&set, 33);
-#  endif
-#  if SANITIZER_LINUX
+  KeepUnblocked(newset, currentset, 33);
+#    endif  // !SANITIZER_ANDROID
+
   // Seccomp-BPF-sandboxed processes rely on SIGSYS to handle trapped syscalls.
   // If this signal is blocked, such calls cannot be handled and the process may
   // hang.
-  internal_sigdelset(&set, 31);
+  KeepUnblocked(newset, currentset, 31);
 
+#    if !SANITIZER_ANDROID
   // Don't block synchronous signals
-  internal_sigdelset(&set, SIGSEGV);
-  internal_sigdelset(&set, SIGBUS);
-  internal_sigdelset(&set, SIGILL);
-  internal_sigdelset(&set, SIGTRAP);
-  internal_sigdelset(&set, SIGABRT);
-  internal_sigdelset(&set, SIGFPE);
-  internal_sigdelset(&set, SIGPIPE);
-#  endif
+  // but also don't unblock signals that the user had deliberately blocked.
+  // FIXME: https://github.com/google/sanitizers/issues/1816
+  KeepUnblocked(newset, currentset, SIGSEGV);
+  KeepUnblocked(newset, currentset, SIGBUS);
+  KeepUnblocked(newset, currentset, SIGILL);
+  KeepUnblocked(newset, currentset, SIGTRAP);
+  KeepUnblocked(newset, currentset, SIGABRT);
+  KeepUnblocked(newset, currentset, SIGFPE);
+  KeepUnblocked(newset, currentset, SIGPIPE);
+#    endif  //! SANITIZER_ANDROID
+
+#  endif  // SANITIZER_LINUX
 
-  SetSigProcMask(&set, oldset);
+  SetSigProcMask(&newset, oldset);
 }
 
 ScopedBlockSignals::ScopedBlockSignals(__sanitizer_sigset_t *copy) {
diff --git a/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt b/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
index 2b4c15125263a9..fef8bb772e0e0d 100644
--- a/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
+++ b/compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt
@@ -15,6 +15,7 @@ set(SANITIZER_UNITTESTS
   sanitizer_array_ref_test.cpp
   sanitizer_atomic_test.cpp
   sanitizer_bitvector_test.cpp
+  sanitizer_block_signals.cpp
   sanitizer_bvgraph_test.cpp
   sanitizer_chained_origin_depot_test.cpp
   sanitizer_common_test.cpp
diff --git a/compiler-rt/lib/sanitizer_common/tests/sanitizer_block_signals.cpp b/compiler-rt/lib/sanitizer_common/tests/sanitizer_block_signals.cpp
new file mode 100644
index 00000000000000..b43648a8aef230
--- /dev/null
+++ b/compiler-rt/lib/sanitizer_common/tests/sanitizer_block_signals.cpp
@@ -0,0 +1,76 @@
+//===-- sanitizer_block_signals.cpp ---------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of sanitizer_common unit tests.
+//
+//===----------------------------------------------------------------------===//
+#include <signal.h>
+#include <stdio.h>
+
+#include "gtest/gtest.h"
+#include "sanitizer_common/sanitizer_linux.h"
+
+namespace __sanitizer {
+
+#if SANITIZER_LINUX && !SANITIZER_ANDROID
+volatile int received_sig = -1;
+
+void signal_handler(int signum) { received_sig = signum; }
+
+TEST(SanitizerCommon, NoBlockSignals) {
+  // No signals blocked
+  signal(SIGUSR1, signal_handler);
+  raise(SIGUSR1);
+  EXPECT_EQ(received_sig, SIGUSR1);
+
+  received_sig = -1;
+  signal(SIGPIPE, signal_handler);
+  raise(SIGPIPE);
+  EXPECT_EQ(received_sig, SIGPIPE);
+}
+
+TEST(SanitizerCommon, BlockSignalsPlain) {
+  // ScopedBlockSignals; SIGUSR1 should be blocked but not SIGPIPE
+  {
+    __sanitizer_sigset_t sigset = {};
+    ScopedBlockSignals block(&sigset);
+
+    received_sig = -1;
+    signal(SIGUSR1, signal_handler);
+    raise(SIGUSR1);
+    EXPECT_EQ(received_sig, -1);
+
+    received_sig = -1;
+    signal(SIGPIPE, signal_handler);
+    raise(SIGPIPE);
+    EXPECT_EQ(received_sig, SIGPIPE);
+  }
+  EXPECT_EQ(received_sig, SIGUSR1);
+}
+
+TEST(SanitizerCommon, BlockSignalsExceptPipe) {
+  // Manually block SIGPIPE; ScopedBlockSignals should not unblock this
+  sigset_t block_sigset;
+  sigemptyset(&block_sigset);
+  sigaddset(&block_sigset, SIGPIPE);
+  sigprocmask(SIG_BLOCK, &block_sigset, NULL);
+  {
+    __sanitizer_sigset_t sigset = {};
+    ScopedBlockSignals block(&sigset);
+
+    received_sig = -1;
+    signal(SIGPIPE, signal_handler);
+    raise(SIGPIPE);
+    EXPECT_EQ(received_sig, -1);
+  }
+  sigprocmask(SIG_UNBLOCK, &block_sigset, NULL);
+  EXPECT_EQ(received_sig, SIGPIPE);
+}
+#endif  // SANITIZER_LINUX && !SANITIZER_ANDROID
+
+}  // namespace __sanitizer

``````````

</details>


https://github.com/llvm/llvm-project/pull/116670