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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" X-Spam-Status: No, score=-11.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 From: Tze Yee Ng An open /dev/mtdX can outlive driver unbind. The MTD core keeps mtd_info registered until the last close, but a spi_nor allocated with devm_*() on the SPI device is already freed, so a later close, ioctl, read or mtdblock flush uses freed memory. v2 moved the lifetime into the MTD core (mtd->_free and mtd->removed). Review pointed out that this creates new problems in the core: the master can be freed inside __put_mtd_device() while it is still used, the driver object leaks when CONFIG_MTD_PARTITIONED_MASTER is off, and a lockless removed check races with remove(). Only spi-nor needs the fix, so v3 goes back to a spi-nor-local kref and reduces the core change to one reorder: - Patch 1: in __put_mtd_device(), call ->_put_device() first and drop the module reference last, so the owner module stays pinned while ->_put_device() frees the driver object. - Patch 2: on the spi-mem path, allocate spi_nor, params, erase regions and the bounce buffer with kmalloc and refcount spi_nor (one reference for registration plus one per open handle). remove() unregisters debugfs and the MTD device, then sets nor->removed under the nor lock; prep_and_lock*() re-check it under the lock and return -ENODEV. Legacy controllers keep the devres lifetime. Not covered: - A sysfs file held open across unbind is a core lifetime question for all MTD drivers and is left out of this series. --- Changes in v3: - Drop the core _free/removed hooks. Patch 1 is only the module_put() reorder. - Patch 2: spi-nor kref again, removed re-checked under the lock, controller module cached at probe, debugfs and MTD unregistered at the start of remove() so mtdblock can flush, eraseregions leak and probe error paths fixed. Changes in v2: - Drop the unrelated RWW self-deadlock fix. - New patch 1: MTD-core _free / removed hooks. - Patch 2: drop the spi-nor kref / refcounted / controller_module and the prep_and_lock*() removed checks; use the core hooks. Also keep eraseregions on that lifetime, free on the probe error path, and unregister debugfs from _free. v2: https://lore.kernel.org/all/cover.1791512623.git.tze.yee.ng@altera.com/ Tze Yee Ng (2): mtd: core: drop the module reference after ->_put_device() mtd: spi-nor: fix use-after-free on unbind with open handles drivers/mtd/mtdcore.c | 9 +- drivers/mtd/spi-nor/core.c | 173 +++++++++++++++++++++++++++------- drivers/mtd/spi-nor/core.h | 2 + drivers/mtd/spi-nor/debugfs.c | 9 +- include/linux/mtd/spi-nor.h | 9 ++ 5 files changed, 159 insertions(+), 43 deletions(-) -- 2.43.7 ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/