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 <[email protected]>
Cc: [email protected] # v2.6.38+
Acked-by: Thomas Gleixner <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Darren Hart <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/kernel/futex.c b/kernel/futex.c
index 80ba086f021d3022afcf3f06ecdb1d920cdc8f7c..02febad007944ca0ff7eaf4880df7f8e06f5972c 100644 (file)
--- 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