[Libguestfs] [PATCH libnbd] states: connect_command: Don't set O_NONBLOCK on socket passed to child.

[Eric Blake]

On 5/25/19 3:22 PM, Eric Blake wrote:
> On 5/25/19 1:33 PM, Richard W.M. Jones wrote:
>> I also made the code a bit more robust about closing the socket along
>> error paths.
>> ---
>>  generator/states-connect.c | 21 ++++++++++++++++++---
>>  1 file changed, 18 insertions(+), 3 deletions(-)
>>
> 
>>    assert (!h->sock);
>>    assert (h->argv);
>>    assert (h->argv[0]);
>> -  if (socketpair (AF_UNIX, SOCK_STREAM|SOCK_NONBLOCK|SOCK_CLOEXEC, 0,
>> -                  sv) == -1) {
>> +  if (socketpair (AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0, sv) == -1) {
> 
> Is it any easier to keep SOCK_NONBLOCK here and then clear O_NONBLOCK in
> the child process? It may matter if we try to port to a system that
> lacks SOCK_CLOEXEC (SOCK_NONBLOCK and SOCK_CLOEXEC were added at the
> same time).  But we can deal with portability when someone reports a
> problem. For now the patch looks fine.

Hmm. Your use of SOCK_CLOEXEC here made me look for other fds that we
might inadvertently destroy or leak in a multi-threaded process that
does fork/exec (or even if the program linking against libnbd does
connect_command() in two separate threads on two different nbd objects).
 I found:
lib/crypto.c: fp = fopen (pskfile, "r");

We need to use either fopen(pskfile, "re") (if libc is new-enough to
support "e" for O_CLOEXEC) or raw open(O_CLOEXEC) + fdopen() instead.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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