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From:   Vasily Averin <vvs@virtuozzo.com>
Subject: [PATCH] memory leaks triggered by perf --namespace
To:     linux-kernel@vger.kernel.org,
        Hari Bathini <hbathini@linux.vnet.ibm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc:     Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>
Message-ID: <c510711b-3904-e5e1-d296-61273d21118d@virtuozzo.com>
Date:   Wed, 15 Nov 2017 08:47:02 +0300
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perf with --namespace key leaks various memory objects including namespaces

# uname -r
4.14.0+
# perf record  -q  --namespace unshare -n -U  -p --fork true
# grep namespace /proc/slabinfo
pid_namespace          1     12   2568   12    8 
user_namespace         1     39    824   39    8 
net_namespace          1      5   6272    5    8 

This happen because perf_fill_ns_link_info() struct patch ns_path:
during initialization ns_path incremented counters on related mnt and dentry,
but without lost path_put nobody decremented them back.
Leaked dentry is name of related namespace,
and its leak does not allow to free unused namespace.

Fixes: commit e422267322cd ("perf: Add PERF_RECORD_NAMESPACES to include namespaces related info")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
 kernel/events/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 10cdb9c..ab5ac84 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6756,6 +6756,7 @@ static void perf_fill_ns_link_info(struct perf_ns_link_info *ns_link_info,
 		ns_inode = ns_path.dentry->d_inode;
 		ns_link_info->dev = new_encode_dev(ns_inode->i_sb->s_dev);
 		ns_link_info->ino = ns_inode->i_ino;
+		path_put(&ns_path);
 	}
 }
 
-- 
2.7.4


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