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bh=ZWWI630ihqLttfdEKhQ55bkwJEf504KdujInZX4vcy0=; b=3QXk5/IVP8lb0s78wOTJJtS7ePy41TuXY8htij3tYUkJteL5ovSbAvTXYgg9iCMLC9 lIs2PXZysxLMPs7dZ6Zq7RPaBfdIGEMuSW8T4VKTY2JAHalcxNg9/t+JMFdKLIHuq+0E 4xEGF5UmSt5PQxR5ghFKqFhX+5B6jGX96E99aQ5MJqAETenJxKEBGnNDWdGtufpMwH4W cPl/ls5GgmZPjBgvEmXo2QfIfwyBw0arQ7OYeThp8l+DpY4mrcgHCwCRpCPvQeNGPyal edob+YW7Y2Y6LzIBkArDBc9Fm532kRLfKwyNDm+DHTQBcLoJBeStkAAvi/10/1J2YtAL Yhvg== X-Gm-Message-State: ANoB5pnwb8jwkUaKcnodRJW39FT+a+/lwLTqQVxdEz97Nz+v1OBRdH5P eAZct3ibRO5i2z4jdamARDAs3Q== X-Received: by 2002:a7b:c008:0:b0:3cf:a85d:2ab2 with SMTP id c8-20020a7bc008000000b003cfa85d2ab2mr38181487wmb.43.1669899569901; Thu, 01 Dec 2022 04:59:29 -0800 (PST) Received: from brgl-uxlite.home ([2a01:cb1d:334:ac00:26bb:b860:c227:f05d]) by smtp.gmail.com with ESMTPSA id v14-20020a05600c444e00b003a1980d55c4sm9564753wmn.47.2022.12.01.04.59.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Dec 2022 04:59:29 -0800 (PST) From: Bartosz Golaszewski To: Kent Gibson , Linus Walleij , Andy Shevchenko Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: [PATCH v6 0/2] gpiolib: don't allow user-space to crash the kernel with hot-unplugs Date: Thu, 1 Dec 2022 13:59:26 +0100 Message-Id: <20221201125928.3031325-1-brgl@bgdev.pl> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1751016852190177677?= X-GMAIL-MSGID: =?utf-8?q?1751016864619373416?= From: Bartosz Golaszewski This is (hopefully) the final iteration of the changes that aim at fixing the situation in which the user-space can provoke a NULL-pointer derefence in the kernel when a GPIO device that's in use by user-space is removed. v5 -> v6: - signal an error in poll callbacks instead of returning 0 which would make the user-space assume a timeout occurred (which could lead to user-space spinning a timeout loop forever) v4 -> v5: - try to acquire the semaphore for reading and bail out of syscall callbacks immediately in case of lock contention v3 -> v4: - use function typedefs to make code cleaner - add a blank line after down_write() v2 -> v3: - drop the helper variable in patch 1/2 as we won't be using it in 2/2 - refactor patch 2/2 to use locking wrappers around the syscall callbacks v1 -> v2: - add missing gdev->chip checks in patch 1/2 - add a second patch that protects the structures that can be accessed by user-space calls against concurrent removal Bartosz Golaszewski (2): gpiolib: cdev: fix NULL-pointer dereferences gpiolib: protect the GPIO device against being dropped while in use by user-space drivers/gpio/gpiolib-cdev.c | 193 ++++++++++++++++++++++++++++++++---- drivers/gpio/gpiolib.c | 4 + drivers/gpio/gpiolib.h | 5 + 3 files changed, 180 insertions(+), 22 deletions(-)