From: Mark Andrews <marka@isc.org>
Date: Sun, 21 Feb 2021 21:44:31 +0000 (+1100)
Subject: Address unbalanced lock/unlock
X-Git-Tag: v9.17.11~26^2
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=3ac53daa065dc67bee8ce60d2365bfbe3d0ca3b4;p=thirdparty%2Fbind9.git

Address unbalanced lock/unlock

Also address race between reading and testing mpctx->allocated
and incrementing mpctx->allocated.
---

diff --git a/lib/isc/mem.c b/lib/isc/mem.c
index 53ea7e6e3ac..9291d896308 100644
--- a/lib/isc/mem.c
+++ b/lib/isc/mem.c
@@ -1306,15 +1306,15 @@ isc__mempool_get(isc_mempool_t *mpctx FLARG) {
 
 	element *item;
 	unsigned int i;
-	size_t allocated = atomic_load_acquire(&mpctx->allocated);
+	size_t allocated = atomic_fetch_add_release(&mpctx->allocated, 1);
 	size_t maxalloc = atomic_load_acquire(&mpctx->maxalloc);
 
 	/*
 	 * Don't let the caller go over quota
 	 */
 	if (ISC_UNLIKELY(allocated >= maxalloc)) {
-		item = NULL;
-		goto out;
+		atomic_fetch_sub_release(&mpctx->allocated, 1);
+		return (NULL);
 	}
 
 	MPCTXLOCK(mpctx);
@@ -1339,6 +1339,7 @@ isc__mempool_get(isc_mempool_t *mpctx FLARG) {
 	 */
 	item = mpctx->items;
 	if (ISC_UNLIKELY(item == NULL)) {
+		atomic_fetch_sub_release(&mpctx->allocated, 1);
 		goto out;
 	}
 
@@ -1346,13 +1347,12 @@ isc__mempool_get(isc_mempool_t *mpctx FLARG) {
 
 	INSIST(atomic_fetch_sub_release(&mpctx->freecount, 1) > 0);
 	atomic_fetch_add_relaxed(&mpctx->gets, 1);
-	atomic_fetch_add_relaxed(&mpctx->allocated, 1);
+
+	ADD_TRACE(mpctx->mctx, item, mpctx->size, file, line);
 
 out:
 	MPCTXUNLOCK(mpctx);
 
-	ADD_TRACE(mpctx->mctx, item, mpctx->size, file, line);
-
 	return (item);
 }