tree 00eaa149d0e9ad3be0848e6b3001236619329e3d
parent 2ef44a3c1a32656dbae30cd16ec5c22a996a4ca9
author Davidlohr Bueso <dave@stgolabs.net> 1527284850 -0700
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1527659417 +0200

ipc/shm: fix shmat() nil address after round-down when remapping

commit 8f89c007b6dec16a1793cb88de88fcc02117bbbc upstream.

shmat()'s SHM_REMAP option forbids passing a nil address for; this is in
fact the very first thing we check for.  Andrea reported that for
SHM_RND|SHM_REMAP cases we can end up bypassing the initial addr check,
but we need to check again if the address was rounded down to nil.  As
of this patch, such cases will return -EINVAL.

Link: http://lkml.kernel.org/r/20180503204934.kk63josdu6u53fbd@linux-n805
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>