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Thu, 15 Oct 2026 08:07:35 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 511171955F10; Thu, 15 Oct 2026 08:07:34 +0000 (UTC) Date: Thu, 15 Oct 2026 09:07:30 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Filip Hejsek Cc: qemu-devel@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Paolo Bonzini Subject: Re: [PATCH v2 2/2] io: report a warning when a file channel is created from a stdio fd Message-ID: References: <20261015-fix-stdio-close-v2-0-0f01e6580e24@gmail.com> <20261015-fix-stdio-close-v2-2-0f01e6580e24@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20261015-fix-stdio-close-v2-2-0f01e6580e24@gmail.com> User-Agent: Mutt/2.4.2 (2026-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 10 X-Spam_score: 1.0 X-Spam_bar: + X-Spam_report: (1.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.24, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Oct 15, 2026 at 03:58:25AM +0200, Filip Hejsek wrote: > A channel closes its fd when the last reference to it is dropped. > Closing stdio fds is typically unwanted, so warn when they are passed to > qio_channel_file_new_fd(). > > Signed-off-by: Filip Hejsek > --- > io/channel-file.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/io/channel-file.c b/io/channel-file.c > index 5cef75a67c..4c9da6619b 100644 > --- a/io/channel-file.c > +++ b/io/channel-file.c > @@ -23,6 +23,7 @@ > #include "io/channel-util.h" > #include "io/channel-watch.h" > #include "qapi/error.h" > +#include "qemu/error-report.h" > #include "qemu/module.h" > #include "qemu/sockets.h" > #include "trace.h" > @@ -32,6 +33,11 @@ qio_channel_file_new_fd(int fd) > { > QIOChannelFile *ioc; > > + if (fd <= STDERR_FILENO) { > + warn_report("potential bug: creating a channel from stdio fd %d; " > + "the fd will be closed when the channel is destroyed", fd); > + } > + > ioc = QIO_CHANNEL_FILE(object_new(TYPE_QIO_CHANNEL_FILE)); > > ioc->fd = fd; Can we also update the API docs for qio_channel_file_new_fd, to say @fd must not point to stdin/stdout/stderr, since the FD will be closed by the channel on destruction. If requiring a channel to wrap stdio, use qio_channel_file_new_dupfd() instead. With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|