daemon: Ensure proper alignment on the stack.

* nix/libstore/build.cc (startBuilder): When calling 'clone', increase
the step to 16 and ensure it aligns properly on the stack.
This commit is contained in:
Efraim Flashner 2017-02-14 21:48:30 +02:00
parent 3b254d7613
commit ab4ccc8fcf
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@ -26,6 +26,7 @@
#include <errno.h>
#include <stdio.h>
#include <cstring>
#include <stdint.h>
#include <pwd.h>
#include <grp.h>
@ -2008,7 +2009,11 @@ void DerivationGoal::startBuilder()
char stack[32 * 1024];
int flags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | CLONE_NEWUTS | SIGCHLD;
if (!fixedOutput) flags |= CLONE_NEWNET;
pid = clone(childEntry, stack + sizeof(stack) - 8, flags, this);
/* Ensure proper alignment on the stack. On aarch64, it has to be 16
bytes. */
pid = clone(childEntry, (char *)(((uintptr_t)stack + 16) & ~0xf),
flags, this);
if (pid == -1)
throw SysError("cloning builder process");
} else