BUG/MINOR: pools: make DEBUG_UAF always write to the to-be-freed location

Since the code was reorganized, DEBUG_UAF was still tested in the locked
pool code despite pools being disabled when DEBUG_UAF is used. Let's move
the test to pool_put_to_os() which is the one that is always called in
this condition.

The impact is only a possible misleading analysis during a troubleshooting
session due to a missing double-frees or free of const area test that is
normally already dealt with by the underlying code anyway. In practice it's
unlikely anyone will ever notice.

This should only be backported to 2.4.

diff --git a/include/haproxy/pool.h b/include/haproxy/pool.h
index 4d13d4c2f88119f42cd66464b20bd8672be166fd..5cbd84cf598ac441961a9bdd33a8931ee5ed7c28 100644 (file)
--- a/include/haproxy/pool.h
+++ b/include/haproxy/pool.h
@@ -194,8 +194,6 @@ static inline void pool_put_to_shared_cache(struct pool_head *pool, void *ptr)
 {
        _HA_ATOMIC_DEC(&pool->used);
 
-#ifndef DEBUG_UAF /* normal pool behaviour */
-
        HA_SPIN_LOCK(POOL_LOCK, &pool->lock);
        if (!pool_is_crowded(pool)) {
                *POOL_LINK(pool, ptr) = (void *)pool->free_list;
@@ -204,13 +202,6 @@ static inline void pool_put_to_shared_cache(struct pool_head *pool, void *ptr)
        }
        HA_SPIN_UNLOCK(POOL_LOCK, &pool->lock);
 
-#else
-       /* release the entry for real to detect use after free */
-       /* ensure we crash on double free or free of a const area */
-       *(uint32_t *)ptr = 0xDEADADD4;
-
-#endif /* DEBUG_UAF */
-
        if (ptr) {
                /* still not freed */
                pool_put_to_os(pool, ptr);

diff --git a/src/pool.c b/src/pool.c
index 827cab457d5fb33018134f22dc9f59e045661331..d788c6168ac19124d886951f9a3c58b741483bcb 100644 (file)
--- a/src/pool.c
+++ b/src/pool.c
@@ -147,6 +147,14 @@ void *pool_get_from_os(struct pool_head *pool)
  */
 void pool_put_to_os(struct pool_head *pool, void *ptr)
 {
+#ifdef DEBUG_UAF
+       /* This object will be released for real in order to detect a use after
+        * free. We also force a write to the area to ensure we crash on double
+        * free or free of a const area.
+        */
+       *(uint32_t *)ptr = 0xDEADADD4;
+#endif /* DEBUG_UAF */
+
        pool_free_area(ptr, pool->size + POOL_EXTRA);
        _HA_ATOMIC_DEC(&pool->allocated);
 }