Commit ce2ae53b authored Jul 10, 2009 by Sonny Rao Committed by Ingo Molnar Jul 11, 2009

futexes: Fix infinite loop in get_futex_key() on huge page



get_futex_key() can infinitely loop if it is called on a
virtual address that is within a huge page but not aligned to
the beginning of that page.  The call to get_user_pages_fast
will return the struct page for a sub-page within the huge page
and the check for page->mapping will always fail.

The fix is to call compound_head on the page before checking
that it's mapped.

Signed-off-by: Sonny Rao <sonnyrao@us.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
Cc: anton@samba.org
Cc: rajamony@us.ibm.com
Cc: speight@us.ibm.com
Cc: mstephen@us.ibm.com
Cc: grimm@us.ibm.com
Cc: mikey@ozlabs.au.ibm.com
LKML-Reference: <20090710231313.GA23572@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent f00caa76

kernel/futex.c

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -247,6 +247,7 @@ again:
	if (err < 0)		if (err < 0)
	return err;		return err;

			page = compound_head(page);
	lock_page(page);		lock_page(page);
	if (!page->mapping) {		if (!page->mapping) {
	unlock_page(page);		unlock_page(page);

Admin message