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Revive running builds in a PID namespace

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This commit is contained in:
Eelco Dolstra 2014-12-23 17:25:06 +01:00
parent f16b8786a2
commit bd0f362d2f
1 changed files with 59 additions and 30 deletions
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89
src/libstore/build.cc
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@ -1586,6 +1586,13 @@ void chmod_(const Path & path, mode_t mode)
}
int childEntry(void * arg)
{
((DerivationGoal *) arg)->runChild();
return 1;
}
void DerivationGoal::startBuilder()
{
startNest(nest, lvlInfo, format(
@ -1902,11 +1909,58 @@ void DerivationGoal::startBuilder()
builderOut.create();
/* Fork a child to build the package. */
ProcessOptions options;
options.allowVfork = !buildUser.enabled();
pid = startProcess([&]() {
runChild();
}, options);
if (useChroot) {
/* Set up private namespaces for the build:
- The PID namespace causes the build to start as PID 1.
Processes outside of the chroot are not visible to those
on the inside, but processes inside the chroot are
visible from the outside (though with different PIDs).
- The private mount namespace ensures that all the bind
mounts we do will only show up in this process and its
children, and will disappear automatically when we're
done.
- The private network namespace ensures that the builder
cannot talk to the outside world (or vice versa). It
only has a private loopback interface.
- The IPC namespace prevents the builder from communicating
with outside processes using SysV IPC mechanisms (shared
memory, message queues, semaphores). It also ensures
that all IPC objects are destroyed when the builder
exits.
- The UTS namespace ensures that builders see a hostname of
localhost rather than the actual hostname.
We use a helper process to do the clone() to work around
clone() being broken in multi-threaded programs due to
at-fork handlers not being run. Note that we use
CLONE_PARENT to ensure that the real builder is parented to
us.
*/
Pid helper = startProcess([&]() {
char stack[32 * 1024];
pid_t child = clone(childEntry, stack + sizeof(stack) - 8,
CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_PARENT | SIGCHLD, this);
if (child == -1) throw SysError("cloning builder process");
writeFull(builderOut.writeSide, int2String(child) + "\n");
_exit(0);
});
if (helper.wait(true) != 0)
throw Error("unable to start build process");
pid_t tmp;
if (!string2Int<pid_t>(readLine(builderOut.readSide), tmp)) abort();
pid = tmp;
} else {
ProcessOptions options;
options.allowVfork = !buildUser.enabled();
pid = startProcess([&]() {
runChild();
}, options);
}
/* parent */
pid.setSeparatePG(true);
@ -1922,7 +1976,6 @@ void DerivationGoal::startBuilder()
printMsg(lvlError, format("@ build-started %1% - %2% %3%")
% drvPath % drv.platform % logFile);
}
}
@ -1938,30 +1991,6 @@ void DerivationGoal::runChild()
#if CHROOT_ENABLED
if (useChroot) {
/* Set up private namespaces for the build:
- The private mount namespace ensures that all the bind
mounts we do will only show up in this process and
its children, and will disappear automatically when
we're done.
- The private network namespace ensures that the
builder cannot talk to the outside world (or vice
versa). It only has a private loopback interface.
- The IPC namespace prevents the builder from
communicating with outside processes using SysV IPC
mechanisms (shared memory, message queues,
semaphores). It also ensures that all IPC objects
are destroyed when the builder exits.
- The UTS namespace ensures that builders see a
hostname of localhost rather than the actual
hostname.
*/
if (unshare(CLONE_NEWNS | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUTS) == -1)
throw SysError("setting up private namespaces");
/* Initialise the loopback interface. */
AutoCloseFD fd(socket(PF_INET, SOCK_DGRAM, IPPROTO_IP));
if (fd == -1) throw SysError("cannot open IP socket");