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Re: [Qemu-devel] [PATCH 18/34] qcow2: Fix memory leak in qcow2_update_op

From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH 18/34] qcow2: Fix memory leak in qcow2_update_options() error path
Date: Wed, 13 May 2015 13:52:39 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0

On 08.05.2015 19:21, Kevin Wolf wrote:
Signed-off-by: Kevin Wolf <address@hidden>
  block/qcow2.c | 12 ++++++++++--
  1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index abe22f3..84d6e0f 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -546,8 +546,8 @@ static int qcow2_update_options(BlockDriverState *bs, QDict 
      const char *opt_overlap_check, *opt_overlap_check_template;
      int overlap_check_template = 0;
      uint64_t l2_cache_size, refcount_cache_size;
-    Qcow2Cache* l2_table_cache;
-    Qcow2Cache* refcount_block_cache;
+    Qcow2Cache* l2_table_cache = NULL;
+    Qcow2Cache* refcount_block_cache = NULL;
      bool use_lazy_refcounts;
      int i;
      Error *local_err = NULL;
@@ -670,6 +670,14 @@ static int qcow2_update_options(BlockDriverState *bs, 
QDict *options,
ret = 0;
+    if (ret < 0) {
+        if (l2_table_cache) {
+            qcow2_cache_destroy(bs, l2_table_cache);
+        }
+        if (refcount_block_cache) {
+            qcow2_cache_destroy(bs, refcount_block_cache);
+        }
+    }
      opts = NULL;

Why don't you squash this into patch 17 (I guess there is a reason, but I fail to see it)?

Also, I think it might make sense to either set {l2_table,refcount_block}_cache to NULL once they have been moved to s->{l2_table,refcount_block}_cache, or, even better, exchange them with their respective field in *s. Thus, you could drop the "if (ret < 0)", I think I'd find the code easier to read, and with the transation, we'd even be safe if the options had been set before and are now to be updated.

But since nothing is wrong:

Reviewed-by: Max Reitz <address@hidden>

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