31c5755caf
commit 582b4e55403e053d8a48ff687a05174da9cc3fb0 upstream.
On s390 there currently is no implementation of pud_write(). That was ok
as long as we had our own implementation of get_user_pages_fast() which
checked for pud protection by testing the bit directly w/o using
pud_write(). The other callers of pud_write() are not reachable on s390.
After commit 1a42010cdc26 ("s390/mm: convert to the generic
get_user_pages_fast code") we use the generic get_user_pages_fast(), which
does call pud_write() in pud_access_permitted() for FOLL_WRITE access on
a large pud. Without an s390 specific pud_write(), the generic version is
called, which contains a BUG() statement to remind us that we don't have a
proper implementation. This results in a kernel panic.
Fix this by providing an implementation of pud_write().
Cc: <stable@vger.kernel.org> # 5.2+
Fixes: 1a42010cdc26 ("s390/mm: convert to the generic get_user_pages_fast code")
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.