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[185.47.220.165]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a1bd96f9a0sm179876155e9.1.2026.10.16.16.09.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Oct 2026 16:09:31 -0700 (PDT) From: Filip Hejsek Subject: [PATCH v3 0/2] io: make sure we don't close stdio fds Date: Sat, 17 Oct 2026 01:09:07 +0200 Message-Id: <20261017-fix-stdio-close-v3-0-cfff0122a2a4@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAAAAAAAC/2WN0Q6CIBhGX8VxHQ0Q0LrqPVoXir/6N5MGxmrOd w9sbW5enu0755uJB4fgyTmbiYOAHu0YIT9kxPTV2AHFJjIRTGjOuKAtvqmfGrTUDNYDPZWllky pRhY5idbTQZysxevtx/5V38FMKZMWPfrJus96GXja/ev5rh44ZVSCaSvJtSlqc+keFQ5HYx8k1 YPY+mrvi+izlnHQqmQg5NZfluUL7sejIwABAAA= X-Change-ID: 20261012-fix-stdio-close-98864055d473 To: qemu-devel@nongnu.org Cc: =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Paolo Bonzini X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1792192170; l=1715; i=filip.hejsek@gmail.com; s=20250912; h=from:subject:message-id; bh=IxoUqjGMEYnmTUe3ybtkcVdXuy1ipY+LkiX7fgZ/l98=; b=GAOQ7/aymYDAorYH22Z/hP8BfX37PNn8judntLLGXbucwPFz9eysnOrM6P/RTsE7i2u9k90Sg isQPkws3uPGCOl6n71I0BMvRZ5IcKZpB6voj/+IirBo8RgSgtOsalrZ X-Developer-Key: i=filip.hejsek@gmail.com; a=ed25519; pk=nakB8gEK3oi+Q/5dBTMCy/LgZL47NP60z1jeDR6O/WU= Received-SPF: pass client-ip=2a00:1450:4864:20::32c; envelope-from=filip.hejsek@gmail.com; helo=mail-wm1-x32c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The stdio chardev currently closes the stdin and stdout fds when it is destroyed. This means that, assuming char0 is a stdio chardev, invoking the HMP command chardev-change char0 null will cause QEMU to run with descriptors 0 and 1 closed. That's not a great situation, as: - the stdio chardev cannot be recreated - code assuming fds 0 and 1 are open will misbehave - the fds 0 and 1 will get assigned to newly opened files, possibly causing them to be confused for actual stdin/stdout The fist patch fixes the problem by duplicating the fds before they get passed to qio_channel_file_new_fd(), the second patch adds a warning that is printed when qio_channel_file_new_fd() is called with a stdio fd and modifies the documentation of that function to say that passing stdio descriptors is incorrect. Changes in v3: - Add documentation changes - Link to v2: https://lore.kernel.org/qemu-devel/20261015-fix-stdio-close-v2-0-0f01e6580e24@gmail.com Changes in v2: - Code style fixes - Set *errp when dup fails - Link to v1: https://lore.kernel.org/qemu-devel/20261013-fix-stdio-close-v1-0-4ecfa416c7bc@gmail.com Signed-off-by: Filip Hejsek --- Filip Hejsek (2): char-stdio: avoid closing stdio fds io: report a warning when a file channel is created from a stdio fd chardev/char-stdio.c | 16 +++++++++++++++- include/io/channel-file.h | 12 ++++++++---- io/channel-file.c | 6 ++++++ 3 files changed, 29 insertions(+), 5 deletions(-) --- base-commit: 7e8d3c7fc460fe7cd28a3e423d7466fa292bc269 change-id: 20261012-fix-stdio-close-98864055d473 Best regards, -- Filip Hejsek