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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
This commit is contained in:
Elliott Hughes 2020-04-23 15:53:17 -07:00
parent c33ad20258
commit 3093e71811
1 changed files with 9 additions and 3 deletions
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12
libc/private/ScopedSignalBlocker.h
View File

@ -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 @@ class ScopedSignalBlocker {
}
void reset() {
sigprocmask64(SIG_SETMASK, &old_set_, nullptr);
__rt_sigprocmask(SIG_SETMASK, &old_set_, nullptr, sizeof(sigset64_t));
}
sigset64_t old_set_;