linux-kernel - [PATCH] memory leaks triggered by perf --namespace

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Date:   Wed, 15 Nov 2017 08:47:02 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     linux-kernel@...r.kernel.org,
        Hari Bathini <hbathini@...ux.vnet.ibm.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH] memory leaks triggered by perf --namespace

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@...tuozzo.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