kernel/linux.git/drivers/misc/nsm.c, branch v7.2-rc5

misc: nsm: pin the module while the device is open

2026-07-17T12:51:57+00:00

misc_open() installs a misc driver's file operations with fops_get(), which pins file_operations::owner before replacing the file's f_op. The NSM misc device leaves nsm_dev_fops.owner unset, so opening /dev/nsm does not take a module reference on the nsm driver. If the driver is built as a module, an open file descriptor can therefore survive rmmod of the module that provides its ioctl callbacks. A later ioctl through that descriptor can call into unloaded module text. Set nsm_dev_fops.owner to THIS_MODULE so the misc core holds the module while any /dev/nsm file descriptor is open, matching the lifetime expectation for the installed file operations. Fixes: b9873755a6c8 ("misc: Add Nitro Secure Module driver") Cc: stable Signed-off-by: Xu Rao Link: https://patch.msgid.link/BE6951D13B5E5513+20260713055523.3193089-1-raoxu@uniontech.com Signed-off-by: Greg Kroah-Hartman

misc: nsm: only unlock nsm_dev on post-lock error paths

2026-07-17T12:51:29+00:00

nsm_dev_ioctl() jumps to the common out label even when the initial copy_from_user() fails before nsm->lock has been taken. The error path then blindly unlocks a mutex that was never acquired. This issue was found by our static analysis tool and then manually reviewed against the current tree. The grounded PoC kept the miscdevice ioctl entry and the pre-lock copy_from_user(&raw, argp, _IOC_SIZE(cmd)) failure path by issuing NSM_IOCTL_RAW with an invalid user pointer. That failure reaches the shared out label before mutex_lock(&nsm->lock). Lockdep reported: WARNING: bad unlock balance detected! exploit/193 is trying to release lock (&global_nsm.lock) at: nsm_dev_ioctl+0x5f/0xcf [vuln_msv] but there are no more locks to release! no locks held by exploit/193. Return immediately on the pre-lock copy_from_user() failure and keep the common unlock label for the post-lock paths only. Fixes: b9873755a6c8 ("misc: Add Nitro Secure Module driver") Cc: stable Signed-off-by: Runyu Xiao Reviewed-by: Alexander Graf Link: https://patch.msgid.link/20260617145350.513875-1-runyu.xiao@seu.edu.cn Signed-off-by: Greg Kroah-Hartman

misc: nsm: drop owner assignment

2024-05-22T12:31:17+00:00

virtio core already sets the .owner, so driver does not need to. Signed-off-by: Krzysztof Kozlowski Message-Id: <20240331-module-owner-virtio-v2-15-98f04bfaf46a@linaro.org> Signed-off-by: Michael S. Tsirkin Reviewed-by: Alexander Graf

misc: Add Nitro Secure Module driver

2023-11-28T19:05:16+00:00

When running Linux inside a Nitro Enclave, the hypervisor provides a special virtio device called "Nitro Security Module" (NSM). This device has 3 main functions: 1) Provide attestation reports 2) Modify PCR state 3) Provide entropy This patch adds a driver for NSM that exposes a /dev/nsm device node which user space can issue an ioctl on this device with raw NSM CBOR formatted commands to request attestation documents, influence PCR states, read entropy and enumerate status of the device. In addition, the driver implements a hwrng backend. Originally-by: Petre Eftime Signed-off-by: Alexander Graf Reviewed-by: Arnd Bergmann Link: https://lore.kernel.org/r/20231011213522.51781-1-graf@amazon.com Signed-off-by: Greg Kroah-Hartman