Public bug reported:
When compiling the following code and executing the program, the child
process hangs forever on a mutex that was held by `getaddrinfo` on
another thread at the time of the fork. I don't see anything in the
manpage for `getaddrinfo` that suggests this shouldn't work. I suspect
glibc is missing a call to `pthread_atfork`.
mre.cpp
```
#include <thread>
#include <netdb.h>
#include <unistd.h>
void spamGetaddrinfo()
{
for (int i = 0; i< 100; ++i)
{
addrinfo *addrInfo{nullptr};
::getaddrinfo("google.com", "80", nullptr, &addrInfo);
}
printf("Thread is done\n");
}
int main()
{
auto thread = std::thread{spamGetaddrinfo};
usleep(1);
if (auto pid = fork(); pid != 0)
{
// Parent
printf("Parent is done\n");
thread.join();
}
else
{
// Child
addrinfo *addrInfo{nullptr};
::getaddrinfo("google.com", "80", nullptr, &addrInfo);
printf("Child is done\n");
}
}
```
Run `g++ -std=c++17 -pthread mre.cpp && ./a.out`
Expected output:
```
Parent is done
Child is done
Thread is done
```
Actual output:
```
Parent is done
Thread is done
```
When finished, use `pkill a.out` to remove the leftover child process.
ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: libc6 2.27-3ubuntu1.5
ProcVersionSignature: Ubuntu 4.15.0-166.174-generic 4.15.18
Uname: Linux 4.15.0-166-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.27
Architecture: amd64
Date: Wed Mar 23 10:32:43 2022
Dependencies:
gcc-8-base 8.4.0-1ubuntu1~18.04
libc6 2.27-3ubuntu1.5
libgcc1 1:8.4.0-1ubuntu1~18.04
InstallationDate: Installed on 2019-12-07 (836 days ago)
InstallationMedia: Ubuntu-Server 18.04.3 LTS "Bionic Beaver" - Release amd64
(20190805)
ProcEnviron:
LANG=en_US.UTF-8
TERM=screen
SHELL=/bin/bash
XDG_RUNTIME_DIR=<set>
PATH=(custom, user)
SourcePackage: glibc
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: glibc (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug bionic uec-images
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https://bugs.launchpad.net/bugs/1966100
Title:
getaddrinfo not fork-safe
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