It is possible for a race to set CACHE_PENDING after cache_clean()
has removed a cache entry from the cache.
If CACHE_PENDING is still set when the entry is finally 'put',
the cache_dequeue() will never happen and we can leak memory.
So set a new flag 'CACHE_CLEANED' when we remove something from
the cache, and don't queue any upcall if it is set.
If CACHE_PENDING is set before CACHE_CLEANED, the call that
cache_clean() makes to cache_fresh_unlocked() will free memory
as needed. If CACHE_PENDING is set after CACHE_CLEANED, the
test in sunrpc_cache_pipe_upcall will ensure that the memory
is not allocated.
Reported-by: <bstroesser@xxxxxxxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
---
include/linux/sunrpc/cache.h | 1 +
net/sunrpc/cache.c | 6 +++++-
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 303399b..8419f7d 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -57,6 +57,7 @@ struct cache_head {
#define CACHE_VALID 0 /* Entry contains valid data */
#define CACHE_NEGATIVE 1 /* Negative entry - there is no match for the key */
#define CACHE_PENDING 2 /* An upcall has been sent but no reply received yet*/
+#define CACHE_CLEANED 3 /* Entry has been cleaned from cache */
#define CACHE_NEW_EXPIRY 120 /* keep new things pending confirmation for 120 seconds */
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 4940be0..454e23c 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -306,7 +306,7 @@ EXPORT_SYMBOL_GPL(cache_check);
* a current pointer into that list and into the table
* for that entry.
*
- * Each time clean_cache is called it finds the next non-empty entry
+ * Each time cache_clean is called it finds the next non-empty entry
* in the current table and walks the list in that entry
* looking for entries that can be removed.
*
@@ -453,6 +453,7 @@ static int cache_clean(void)
current_index ++;
spin_unlock(&cache_list_lock);
if (ch) {
+ set_bit(CACHE_CLEANED, &ch->flags);
cache_fresh_unlocked(ch, d);
cache_put(ch, d);
}
@@ -1178,6 +1179,9 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h)
warn_no_listener(detail);
return -EINVAL;
}
+ if (test_bit(CACHE_CLEANED, &h->flags))
+ /* Too late to make an upcall */
+ return -EAGAIN;
buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!buf)
--
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