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Prevent a deadlock when user namespace setup fails

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Observed on Centos 7 when user namespaces are disabled:
DerivationGoal::startBuilder() throws an exception, ~DerivationGoal()
waits for the child process to exit, but the child process hangs
forever in drainFD(userNamespaceSync.readSide.get()) in
DerivationGoal::runChild(). Not sure why the SIGKILL doesn't get
through.

Issue #4092.
This commit is contained in:
Eelco Dolstra 2020-10-06 18:52:46 +02:00
parent ad143c5b3b
commit d761485010
1 changed files with 6 additions and 1 deletions
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7
src/libstore/build.cc
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@ -2686,6 +2686,12 @@ void DerivationGoal::startBuilder()
userNamespaceSync.readSide = -1;
/* Close the write side to prevent runChild() from hanging
reading from this. */
Finally cleanup([&]() {
userNamespaceSync.writeSide = -1;
});
pid_t tmp;
if (!string2Int<pid_t>(readLine(builderOut.readSide.get()), tmp)) abort();
pid = tmp;
@ -2712,7 +2718,6 @@ void DerivationGoal::startBuilder()
/* Signal the builder that we've updated its user namespace. */
writeFull(userNamespaceSync.writeSide.get(), "1");
userNamespaceSync.writeSide = -1;
} else
#endif