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linux: set ptracer in signal handlers

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Bug: b/215231949
Change-Id: I7e81308ed755d5f9340950fcf6a1bb70fcf66cd6
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/3472607
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
This commit is contained in:
Joshua Peraza 2022-03-03 10:13:48 -08:00 committed by Crashpad LUCI CQ
parent 0affe61689
commit 13202c2ffe
1 changed files with 20 additions and 11 deletions
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31
client/crashpad_client_linux.cc
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@ -351,17 +351,11 @@ class RequestCrashDumpHandler : public SignalHandler {
}
pid = creds.pid;
}
if (pid > 0 && prctl(PR_SET_PTRACER, pid, 0, 0, 0) != 0) {
PLOG(WARNING) << "prctl";
// TODO(jperaza): If this call to set the ptracer failed, it might be
// possible to try again just before a dump request, in case the
// environment has changed. Revisit ExceptionHandlerClient::SetPtracer()
// and consider saving the result of this call in ExceptionHandlerClient
// or as a member in this signal handler. ExceptionHandlerClient hasn't
// been responsible for maintaining state and a new ExceptionHandlerClient
// has been constructed as a local whenever a client needs to communicate
// with the handler. ExceptionHandlerClient lifetimes and ownership will
// need to be reconsidered if it becomes responsible for state.
if (pid > 0) {
pthread_atfork(nullptr, nullptr, SetPtracerAtFork);
if (prctl(PR_SET_PTRACER, pid, 0, 0, 0) != 0) {
PLOG(WARNING) << "prctl";
}
}
sock_to_handler_.reset(sock.release());
handler_pid_ = pid;
@ -382,6 +376,13 @@ class RequestCrashDumpHandler : public SignalHandler {
}
void HandleCrashImpl() override {
// Attempt to set the ptracer again, in case a crash occurs after a fork,
// before SetPtracerAtFork() has been called. Ignore errors because the
// system call may be disallowed if the sandbox is engaged.
if (handler_pid_ > 0) {
sys_prctl(PR_SET_PTRACER, handler_pid_, 0, 0, 0);
}
ExceptionHandlerProtocol::ClientInformation info = {};
info.exception_information_address =
FromPointerCast<VMAddress>(&GetExceptionInfo());
@ -404,6 +405,14 @@ class RequestCrashDumpHandler : public SignalHandler {
~RequestCrashDumpHandler() = delete;
static void SetPtracerAtFork() {
auto handler = RequestCrashDumpHandler::Get();
if (handler->handler_pid_ > 0 &&
prctl(PR_SET_PTRACER, handler->handler_pid_, 0, 0, 0) != 0) {
PLOG(WARNING) << "prctl";
}
}
ScopedFileHandle sock_to_handler_;
pid_t handler_pid_ = -1;