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This wraps os/exec to:
* Clear the environment when the hook doesn't set 'env'. The runtime
spec has [1]:
> * env (array of strings, OPTIONAL) with the same semantics as IEEE
> Std 1003.1-2008's environ.
And running execle or similar with NULL env results in an empty
environment:
$ cat test.c
#include <unistd.h>
int main()
{
return execle("/usr/bin/env", "env", NULL, NULL);
}
$ cc -o test test.c
$ ./test
...no output...
Go's Cmd.Env, on the other hand, has [2]:
> If Env is nil, the new process uses the current process's environment.
This commit works around that by setting []string{} in those cases
to avoid leaking the runtime environment into the hooks.
* Roll the 'timeout' value (if set) into the passed context. There's
no need for two separate ways to cancel hook execution.
* Add a configurable timeout on abandoning a post-kill wait. The
waiting goroutine will continue and eventually reap the process, but
this avoids blocking the Run() call when that takes inordinately
long (for example, if a GPU cleanup hook is stuck in I/O sleep [3]).
The 'env' output format is specified in POSIX [4].
[1]: https://github.com/opencontainers/runtime-spec/blob/v1.0.1/config.md#posix-platform-hooks
[2]: https://golang.org/pkg/os/exec/#Cmd
[3]: https://github.com/projectatomic/libpod/pull/857#discussion_r192191002
[4]: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/env.html
Signed-off-by: W. Trevor King <wking@tremily.us>
Closes: #857
Approved by: mheon
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