From: Darren Hart <dvhltc@us.ibm.com>
Date: Tue, 30 Dec 2008 03:43:21 +0000 (-0800)
Subject: futex: catch certain assymetric (get|put)_futex_key calls
X-Git-Tag: v2.6.29-rc1~226^2^2
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=90621c40cc4ab7b0a414311ce37e7cc7173403b6;p=linux.git

futex: catch certain assymetric (get|put)_futex_key calls

Impact: add debug check

Following up on my previous key reference accounting patches, this patch
will catch puts on keys that haven't been "got".  This won't catch nested
get/put mismatches though.

Build and boot tested, with minimal desktop activity and a run of the
open_posix_testsuite in LTP for testing.  No warnings logged.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/futex.c b/kernel/futex.c
index c5ac55cc0c16..206d4c906885 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -170,8 +170,11 @@ static void get_futex_key_refs(union futex_key *key)
  */
 static void drop_futex_key_refs(union futex_key *key)
 {
-	if (!key->both.ptr)
+	if (!key->both.ptr) {
+		/* If we're here then we tried to put a key we failed to get */
+		WARN_ON_ONCE(1);
 		return;
+	}
 
 	switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
 	case FUT_OFF_INODE: