From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 12 Dec 2013 17:38:42 +0000 (-0800)
Subject: futex: fix handling of read-only-mapped hugepages
X-Git-Tag: drm-fsl-dcu-for-next~6246
X-Git-Url: http://git.agner.ch/gitweb/?p=linux-drm-fsl-dcu.git;a=commitdiff_plain;h=f12d5bfceb7e1f9051563381ec047f7f13956c3c

futex: fix handling of read-only-mapped hugepages

The hugepage code had the exact same bug that regular pages had in
commit 7485d0d3758e ("futexes: Remove rw parameter from
get_futex_key()").

The regular page case was fixed by commit 9ea71503a8ed ("futex: Fix
regression with read only mappings"), but the transparent hugepage case
(added in a5b338f2b0b1: "thp: update futex compound knowledge") case
remained broken.

Found by Dave Jones and his trinity tool.

Reported-and-tested-by: Dave Jones <davej@fedoraproject.org>
Cc: stable@kernel.org # v2.6.38+
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/futex.c b/kernel/futex.c
index 80ba086f021d..02febad00794 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -288,7 +288,7 @@ again:
 		put_page(page);
 		/* serialize against __split_huge_page_splitting() */
 		local_irq_disable();
-		if (likely(__get_user_pages_fast(address, 1, 1, &page) == 1)) {
+		if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) {
 			page_head = compound_head(page);
 			/*
 			 * page_head is valid pointer but we must pin