8f33bb2400
When user deletes a tcmu device via configFS, tcmu calls uio_unregister_device(). During that call uio resets its pointer to struct uio_info provided by tcmu. That means, after uio_unregister_device() uio will no longer execute any of the callbacks tcmu had set in uio_info. Especially, if userspace daemon still holds the corresponding uio device open or mmap'ed while tcmu calls uio_unregister_device(), uio will not call tcmu_release() when userspace finally closes and munmaps the uio device. Since tcmu does refcounting for the tcmu device in tcmu_open() and tcmu_release(), in the decribed case refcount does not drop to 0 and tcmu does not free tcmu device's resources. In extreme cases this can cause memory leaking of up to 1 GB for a single tcmu device. After uio_unregister_device(), uio will reject every open, read, write, mmap from userspace with -EOI. But userspace daemon can still access the mmap'ed command ring and data area. Therefore tcmu should wait until userspace munmaps the uio device before it frees the resources, as we don't want to cause SIGSEGV or SIGBUS to user space. That said, current refcounting during tcmu_open and tcmu_release does not work correctly, and refcounting better should be done in the open and close callouts of the vm_operations_struct, which tcmu assigns to each mmap of the uio device (because it wants its own page fault handler). This patch fixes the memory leak by removing refcounting from tcmu_open and tcmu_close, and instead adding new tcmu_vma_open() and tcmu_vma_close() handlers that only do refcounting. Link: https://lore.kernel.org/r/20210218175039.7829-3-bostroesser@gmail.com Reviewed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Bodo Stroesser <bostroesser@gmail.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.