Al Viro 2527b284de move the capability checks from sget_userns() to legacy_get_tree()
1) all call chains leading to sget_userns() pass through ->mount()
instances.
2) none of ->mount() instances is ever called directly - the only
call site is legacy_get_tree()
3) all remaining ->mount() instances end up calling sget_userns()

IOW, we might as well do the capability checks just before calling
->mount().  As for the arguments passed to mount_capable(),
in case of call chains to sget_userns() going through sget(),
we either don't call mount_capable() at all, or pass current_user_ns()
to it.  The call chains going through mount_pseudo_xattr() don't
call mount_capable() at all (SB_KERNMOUNT in flags on those).

That could've been split into smaller steps (lifting the checks
into sget(), then callers of sget(), then all the way to the
entries of every ->mount() out there, then to the sole caller),
but that would be too much churn for little benefit...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-05-25 17:59:58 -04:00
2019-05-25 17:59:57 -04:00
2019-05-16 15:51:55 -07:00
2019-05-19 15:47:09 -07:00

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.
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