Block all signals in ScopedSignalBlocker.
When a thread calls pthread_exit(3), ScopedSignalBlocker blocks all
user-visible signals, but leaves internal-use signals 33/34/36/36/37.
Signal 33 is used to unwind a thread for a backtrace, which can cause us
to access the stack after it's been unmapped. (Avoiding this was the
reason why we have the ScopedSignalBlocker in pthread_exit(3)!)
Fix this (and other potential issues) by changing ScopedSignalBlocker to
call __rt_sigprocmask(2) directly, so we don't mask out the internal-use
signals.
Bug: https://issuetracker.google.com/153624226
Test: not trivially reproducible
Change-Id: I9b125ed41ddee4c5d33b45920f1d142e52db47cb
diff --git a/libc/private/ScopedSignalBlocker.h b/libc/private/ScopedSignalBlocker.h
index ce0ae64..f6ba9ed 100644
--- a/libc/private/ScopedSignalBlocker.h
+++ b/libc/private/ScopedSignalBlocker.h
@@ -20,20 +20,26 @@
#include "platform/bionic/macros.h"
+// This code needs to really block all the signals, not just the user-visible
+// ones. We call __rt_sigprocmask(2) directly so we don't mask out our own
+// signals (https://issuetracker.google.com/153624226 was a pthread_exit(3)
+// crash because a request to dump the thread's stack came in as it was exiting).
+extern "C" int __rt_sigprocmask(int, const sigset64_t*, sigset64_t*, size_t);
+
class ScopedSignalBlocker {
public:
// Block all signals.
explicit ScopedSignalBlocker() {
sigset64_t set;
sigfillset64(&set);
- sigprocmask64(SIG_BLOCK, &set, &old_set_);
+ __rt_sigprocmask(SIG_BLOCK, &set, &old_set_, sizeof(sigset64_t));
}
// Block just the specified signal.
explicit ScopedSignalBlocker(int signal) {
sigset64_t set = {};
sigaddset64(&set, signal);
- sigprocmask64(SIG_BLOCK, &set, &old_set_);
+ __rt_sigprocmask(SIG_BLOCK, &set, &old_set_, sizeof(sigset64_t));
}
~ScopedSignalBlocker() {
@@ -41,7 +47,7 @@
}
void reset() {
- sigprocmask64(SIG_SETMASK, &old_set_, nullptr);
+ __rt_sigprocmask(SIG_SETMASK, &old_set_, nullptr, sizeof(sigset64_t));
}
sigset64_t old_set_;
