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Merge pull request #1562 from cyphar/carry-975-959-ipc-uid-namespaces 

nsenter: improve namespace creation and SELinux IPC handling
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Mrunal Patel 2018-04-26 14:12:33 -07:00 committed by GitHub
parent 871ba2e58e 5a46c2ba8b
commit 0cbfd8392f
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1 changed files with 31 additions and 13 deletions
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44
libcontainer/nsenter/nsexec.c
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@ -808,25 +808,30 @@ void nsexec(void)
if (config.namespaces)
join_namespaces(config.namespaces);
/*
* Unshare all of the namespaces. Now, it should be noted that this
* ordering might break in the future (especially with rootless
* containers). But for now, it's not possible to split this into
* CLONE_NEWUSER + [the rest] because of some RHEL SELinux issues.
*
* Note that we don't merge this with clone() because there were
* some old kernel versions where clone(CLONE_PARENT | CLONE_NEWPID)
* was broken, so we'll just do it the long way anyway.
*/
if (unshare(config.cloneflags) < 0)
bail("failed to unshare namespaces");
/*
* Deal with user namespaces first. They are quite special, as they
* affect our ability to unshare other namespaces and are used as
* context for privilege checks.
*
* We don't unshare all namespaces in one go. The reason for this
* is that, while the kernel documentation may claim otherwise,
* there are certain cases where unsharing all namespaces at once
* will result in namespace objects being owned incorrectly.
* Ideally we should just fix these kernel bugs, but it's better to
* be safe than sorry, and fix them separately.
*
* A specific case of this is that the SELinux label of the
* internal kern-mount that mqueue uses will be incorrect if the
* UTS namespace is cloned before the USER namespace is mapped.
* I've also heard of similar problems with the network namespace
* in some scenarios. This also mirrors how LXC deals with this
* problem.
*/
if (config.cloneflags & CLONE_NEWUSER) {
if (unshare(CLONE_NEWUSER) < 0)
bail("failed to unshare user namespace");
config.cloneflags &= ~CLONE_NEWUSER;
/*
* We don't have the privileges to do any mapping here (see the
* clone_parent rant). So signal our parent to hook us up.
@ -852,8 +857,21 @@ void nsexec(void)
if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) < 0)
bail("failed to set process as dumpable");
}
/* Become root in the namespace proper. */
if (setresuid(0, 0, 0) < 0)
bail("failed to become root in user namespace");
}
/*
* Unshare all of the namespaces. Note that we don't merge this
* with clone() because there were some old kernel versions where
* clone(CLONE_PARENT | CLONE_NEWPID) was broken, so we'll just do
* it the long way.
*/
if (unshare(config.cloneflags) < 0)
bail("failed to unshare namespaces");
/*
* TODO: What about non-namespace clone flags that we're dropping here?
*