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Calls of do_umount() are always preceded by can_umount(), where we'd done a racy check for mount belonging to our namespace; if it wasn't, can_unmount() would've failed with -EINVAL and we wouldn't have reached do_umount() at all. That check needs to be redone once we have acquired namespace_sem and in do_umount() we do that. However, that's done in a very odd way; we check that mount is still in rbtree of _some_ namespace or its mnt_list is not empty. It is equivalent to check_mnt(mnt) - we know that earlier mnt was mounted in our namespace; if it has stayed there, it's going to remain in rbtree of our namespace. OTOH, if it ever had been removed from out namespace, it would be removed from rbtree and it never would've re-added to a namespace afterwards. As for ->mnt_list, for something that had been mounted in a namespace we'll never observe non-empty ->mnt_list while holding namespace_sem - it does temporarily become non-empty during umount_tree(), but that doesn't outlast the call of umount_tree(), let alone dropping namespace_sem. Things get much easier to follow if we replace that with (equivalent) check_mnt(mnt) there. What's more, currently we treat a failure of that test as "quietly do nothing"; we might as well pretend that we'd lost the race and fail on that the same way can_umount() would have. Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
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| .cocciconfig | ||
| .editorconfig | ||
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| 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.