gpib: fix use-after-free in IO ioctl handlersThe IBRD, IBWRT, IBCMD, and IBWAIT ioctl handlers use a gpib_descriptorpointer after board->big_gpib_mutex has been released. A concurrentIBCLOSEDEV
gpib: fix use-after-free in IO ioctl handlersThe IBRD, IBWRT, IBCMD, and IBWAIT ioctl handlers use a gpib_descriptorpointer after board->big_gpib_mutex has been released. A concurrentIBCLOSEDEV ioctl can free the descriptor via close_dev_ioctl() duringthis window, causing a use-after-free.The IO handlers (read_ioctl, write_ioctl, command_ioctl) explicitlyrelease big_gpib_mutex before calling their handler. wait_ioctl() iscalled with big_gpib_mutex held, but ibwait() releases it internallywhen wait_mask is non-zero. In all four cases, the descriptor pointerobtained from handle_to_descriptor() becomes unprotected.Fix this by introducing a kernel-only descriptor_busy reference countin struct gpib_descriptor. Each handler atomically incrementsdescriptor_busy under file_priv->descriptors_mutex before releasing thelock, and decrements it when done. close_dev_ioctl() checksdescriptor_busy under the same lock and rejects the close with -EBUSYif the count is non-zero.A reference count rather than a simple flag is necessary becausemultiple handlers can operate on the same descriptor concurrently(e.g. IBRD and IBWAIT on the same handle from different threads).A separate counter is needed because io_in_progress can be cleared fromunprivileged userspace via the IBWAIT ioctl (through general_ibstatus()with set_mask containing CMPL), which would allow an attacker to bypassa check based solely on io_in_progress. The new descriptor_busycounter is only modified by the kernel IO paths.The lock ordering is consistent (big_gpib_mutex -> descriptors_mutex)and the handlers only hold descriptors_mutex briefly during the lookup,so there is no deadlock risk and no impact on IO throughput.Signed-off-by: Adam Crosser <adam.crosser@praetorian.com>Cc: stable <stable@kernel.org>Reviewed-by: Dave Penkler <dpenkler@gmail.com>Tested-by: Dave Penkler <dpenkler@gmail.com>Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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staging: gpib: Destage gpibMove the gpib drivers out of staging and into the "real" part of thekernel. This entails: - Remove the gpib Kconfig menu and Makefile build rule from staging. - Remo
staging: gpib: Destage gpibMove the gpib drivers out of staging and into the "real" part of thekernel. This entails: - Remove the gpib Kconfig menu and Makefile build rule from staging. - Remove gpib/uapi from the header file search path in subdir-ccflags of the gpib Makefile - move the gpib/uapi files to include/uapi/linux - Move the gpib tree out of staging to drivers. - Remove the word "Linux" from the gpib Kconfig file. - Add the gpib Kconfig menu and Makefile build rule to driversSigned-off-by: Dave Penkler <dpenkler@gmail.com>Link: https://patch.msgid.link/20251117144021.23569-5-dpenkler@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>