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Simplify the PID namespace check: just try to mount /proc

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Fixes #7783.
This commit is contained in:
Eelco Dolstra 2023-02-10 14:38:14 +01:00
parent 5597d68e2d
commit f094ba7386
5 changed files with 69 additions and 48 deletions
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29
src/libutil/util.cc
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@ -36,6 +36,7 @@
#ifdef __linux__
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/mman.h>
#include <cmath>
#endif
@ -1051,9 +1052,17 @@ static pid_t doFork(bool allowVfork, std::function<void()> fun)
}
static int childEntry(void * arg)
{
auto main = (std::function<void()> *) arg;
(*main)();
return 1;
}
pid_t startProcess(std::function<void()> fun, const ProcessOptions & options)
{
auto wrapper = [&]() {
std::function<void()> wrapper = [&]() {
if (!options.allowVfork)
logger = makeSimpleLogger();
try {
@ -1073,7 +1082,23 @@ pid_t startProcess(std::function<void()> fun, const ProcessOptions & options)
_exit(1);
};
pid_t pid = doFork(options.allowVfork, wrapper);
pid_t pid = -1;
if (options.cloneFlags) {
// Not supported, since then we don't know when to free the stack.
assert(!(options.cloneFlags & CLONE_VM));
size_t stackSize = 1 * 1024 * 1024;
auto stack = (char *) mmap(0, stackSize,
PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
if (stack == MAP_FAILED) throw SysError("allocating stack");
Finally freeStack([&]() { munmap(stack, stackSize); });
pid = clone(childEntry, stack + stackSize, options.cloneFlags | SIGCHLD, &wrapper);
} else
pid = doFork(options.allowVfork, wrapper);
if (pid == -1) throw SysError("unable to fork");
return pid;