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3f05317d98
syzbot reported a use-after-free of shm_file_data(file)->file->f_op in shm_get_unmapped_area(), called via sys_remap_file_pages(). Unfortunately it couldn't generate a reproducer, but I found a bug which I think caused it. When remap_file_pages() is passed a full System V shared memory segment, the memory is first unmapped, then a new map is created using the ->vm_file. Between these steps, the shm ID can be removed and reused for a new shm segment. But, shm_mmap() only checks whether the ID is currently valid before calling the underlying file's ->mmap(); it doesn't check whether it was reused. Thus it can use the wrong underlying file, one that was already freed. Fix this by making the "outer" shm file (the one that gets put in ->vm_file) hold a reference to the real shm file, and by making __shm_open() require that the file associated with the shm ID matches the one associated with the "outer" file. Taking the reference to the real shm file is needed to fully solve the problem, since otherwise sfd->file could point to a freed file, which then could be reallocated for the reused shm ID, causing the wrong shm segment to be mapped (and without the required permission checks). Commit |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| 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 | ||
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.