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![Gerald Schaefer](https://secure.gravatar.com/avatar/da3639a39267e46fad486c328c87eaf5.jpg?s=96&d=mm)
Gerald Schaefer committed 31c5755caf6
s390/mm: fix panic in gup_fast on large pud 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>