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According to the syzbot report referenced here, it is possible to encounter a race between mprotect() writing to the vma->vm_flags field and migration checking whether the VMA is locked. There is no real problem with timing here per se, only that torn reads/writes may occur. Therefore, as a proximate fix, ensure both operations READ_ONCE() and WRITE_ONCE() to avoid this. This race is possible due to the ability to look up VMAs via the rmap, which migration does in this case, which takes no mmap or VMA lock and therefore does not preclude an operation to modify a VMA. When the final update of VMA flags is performed by mprotect, this will cause the rmap lock to be taken while the VMA is inserted on split/merge. However the means by which we perform splits/merges in the kernel is that we perform the split/merge operation on the VMA, acquiring/releasing locks as needed, and only then, after having done so, modifying fields. We should carefully examine and determine whether we can combine the two operations so as to avoid such races, and whether it might be possible to otherwise annotate these rmap field accesses. Link: https://lkml.kernel.org/r/20250207172442.78836-1-lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reported-by: syzbot+c2e5712cbb14c95d4847@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/67a34e60.050a0220.50516.0040.GAE@google.com/ Cc: Jann Horn <jannh@google.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
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| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| 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 reStructuredText 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.