[tip:perf/urgent] perf/core: Fix memory leak triggered by perf --namespace

[tip-bot for Vasily Averin]

Commit-ID:  0e18dd12064e07519f7cbff4149ca7fff620cbed
Gitweb:     https://git.kernel.org/tip/0e18dd12064e07519f7cbff4149ca7fff620cbed
Author:     Vasily Averin <vvs@xxxxxxxxxxxxx>
AuthorDate: Wed, 15 Nov 2017 08:47:02 +0300
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 15 Nov 2017 09:47:27 +0100

perf/core: Fix memory leak triggered by perf --namespace

perf with --namespace key leaks various memory objects including namespaces

  4.14.0+
  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.

Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fixes: commit e422267322cd ("perf: Add PERF_RECORD_NAMESPACES to include namespaces related info")
Link: http://lkml.kernel.org/r/c510711b-3904-e5e1-d296-61273d21118d@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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);
 	}
 }