[Libguestfs] [PATCH v3 libguestfs] launch: Implement a safer getumask.

[Eric Blake]

On 04/14/2016 07:57 AM, Richard W.M. Jones wrote:
> On Thu, Apr 14, 2016 at 07:38:23AM -0600, Eric Blake wrote:
>>> +  /* Read the umask. */
>>> +  if (read (fd[0], &mask, sizeof mask) != sizeof mask) {
>>> +    perrorf (g, "read");
>>> +    close (fd[0]);
>>> +    return -1;
>>
>> Oops - this strands a child process.  You have to reap the child, even
>> if the read() failed.
> 
> Bleah that was stupid.  Try attached version - the only difference is
> I added a waitpid call to the error path above.

But without looping on EINTR...


+
+  /* Read the umask. */
+  if (read (fd[0], &mask, sizeof mask) != sizeof mask) {
+    perrorf (g, "read");
+    close (fd[0]);
+    waitpid (pid, NULL, 0);

I think it's enough to make this line:

    while (waitpid (pid, &status, 0) == -1 && errno == EINTR);

+    return -1;

as you've already reported the initial error, and are merely focused on
cleanup of the child.

+  }
+  close (fd[0]);
+
+ again:
+  if (waitpid (pid, &status, 0) == -1) {
+    if (errno == EINTR) goto again;
+    perrorf (g, "waitpid");
+    return -1;

Anything else, like trying to reuse the again: loop, seems like it be
more complicated control flow.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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