2527b284de
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>
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.