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4a0b33f771
On policy reload selinuxfs replaces two subdirectories (/booleans and /class) with new variants. Unfortunately, that's done with serious abuses of directory locking. 1) lock_rename() should be done to parents, not to objects being exchanged 2) there's a bunch of reasons why it should not be done for directories that do not have a common ancestor; most of those do not apply to selinuxfs, but even in the best case the proof is subtle and brittle. 3) failure halfway through the creation of /class will leak names and values arrays. 4) use of d_genocide() is also rather brittle; it's probably not much of a bug per se, but e.g. an overmount of /sys/fs/selinuxfs/classes/shm/index with any regular file will end up with leaked mount on policy reload. Sure, don't do it, but... Let's stop messing with disconnected directories; just create a temporary (/.swapover) with no permissions for anyone (on the level of ->permission() returing -EPERM, no matter who's calling it) and build the new /booleans and /class in there; then lock_rename on root and that temporary directory and d_exchange() old and new both for class and booleans. Then unlock and use simple_recursive_removal() to take the temporary out; it's much more robust. And instead of bothering with separate pathways for freeing new (on failure halfway through) and old (on success) names/values, do all freeing in one place. With temporaries swapped with the old ones when we are past all possible failures. The only user-visible difference is that /.swapover shows up (but isn't possible to open, look up into, etc.) for the duration of policy reload. Reviewed-by: Stephen Smalley <stephen.smalley.work@gmail.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> [PM: applied some fixes from Al post merge] Signed-off-by: Paul Moore <paul@paul-moore.com> |
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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.