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[34.125.100.95]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b07c896cc6sm6096249a91.9.2026.11.03.14.53.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Nov 2026 14:53:33 -0800 (PST) From: Joseph CT Chan To: Mark Brown Cc: linux-spi@vger.kernel.org, David Lechner , Bart Van Assche , Joseph CT Chan , stable@vger.kernel.org Subject: [PATCH v2 1/5] spi: spi-mux: release mux when parent setup fails Date: Tue, 3 Nov 2026 22:53:04 +0000 Message-ID: <20261103225308.3633046-2-jctchan@gmail.com> X-Mailer: git-send-email 2.56.0.385.gac671c819a-goog In-Reply-To: <20261103225308.3633046-1-jctchan@gmail.com> References: <20261103225308.3633046-1-jctchan@gmail.com> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Joseph CT Chan When spi_mux_select() switches to a different child, it locks the mux with mux_control_select(), copies the child's settings into the spi-mux device and calls spi_setup() on the parent controller. If spi_setup() fails, spi_mux_select() returns the error without calling mux_control_deselect(), so the mux stays locked. The next message on any child of this mux then blocks forever in mux_control_select(), and so does every other user of the same mux control. spi_mux_select() also records the new chip select in current_cs before spi_setup() runs. After a failure, the next message for the same child skips the copy and spi_setup(), and is sent with a parent that was never set up for it. On spi_setup() failure, set current_cs to SPI_MUX_NO_CS, so the next message sets up the parent again, and release the mux. Record the new chip select only after spi_setup() succeeds. Tested with KUnit (spi_mux: spi_mux_error_test, added later in this series) on ARCH=um; that case also needs "spi: spi-mux: finalize message when forwarding fails" to see the error status. Builds with W=1 on x86_64. Not tested on hardware. Developed with help from the Claude and Gemini AI assistants. Fixes: 5a5fc308418a ("spi: spi-mux: Fix coverity issue, unchecked return value") Cc: stable@vger.kernel.org Signed-off-by: Joseph CT Chan --- drivers/spi/spi-mux.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spi-mux.c b/drivers/spi/spi-mux.c index 08fe1fa32dea..28d7718138a5 100644 --- a/drivers/spi/spi-mux.c +++ b/drivers/spi/spi-mux.c @@ -66,9 +66,16 @@ static int spi_mux_select(struct spi_device *spi) priv->spi->mode = spi->mode; priv->spi->bits_per_word = spi->bits_per_word; + ret = spi_setup(priv->spi); + if (ret) { + priv->current_cs = SPI_MUX_NO_CS; + mux_control_deselect(priv->mux); + return ret; + } + priv->current_cs = spi_get_chipselect(spi, 0); - return spi_setup(priv->spi); + return 0; } static int spi_mux_setup(struct spi_device *spi) -- 2.56.0.385.gac671c819a-goog