linux-kernel - [tip:perf/urgent] perf/core: Fix event inheritance on fork()

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Message-ID: <tip-e7cc4865f0f31698ef2f7aac01a50e78968985b7@git.kernel.org>
Date:   Thu, 16 Mar 2017 08:19:57 -0700
From:   tip-bot for Peter Zijlstra <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, alexander.shishkin@...ux.intel.com,
        hpa@...or.com, mingo@...nel.org, eranian@...gle.com,
        jolsa@...hat.com, dvyukov@...gle.com,
        mathieu.desnoyers@...icios.com, peterz@...radead.org,
        acme@...hat.com, linux-kernel@...r.kernel.org, oleg@...hat.com,
        fweisbec@...il.com, vincent.weaver@...ne.edu,
        torvalds@...ux-foundation.org, acme@...nel.org
Subject: [tip:perf/urgent] perf/core: Fix event inheritance on fork()

Commit-ID:  e7cc4865f0f31698ef2f7aac01a50e78968985b7
Gitweb:     http://git.kernel.org/tip/e7cc4865f0f31698ef2f7aac01a50e78968985b7
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Thu, 16 Mar 2017 13:47:49 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 16 Mar 2017 14:16:52 +0100

perf/core: Fix event inheritance on fork()

While hunting for clues to a use-after-free, Oleg spotted that
perf_event_init_context() can loose an error value with the result
that fork() can succeed even though we did not fully inherit the perf
event context.

Spotted-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Cc: oleg@...hat.com
Cc: stable@...r.kernel.org
Fixes: 889ff0150661 ("perf/core: Split context's event group list into pinned and non-pinned lists")
Link: http://lkml.kernel.org/r/20170316125823.190342547@infradead.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/events/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4742909..fc7c9a8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10679,7 +10679,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
 		ret = inherit_task_group(event, parent, parent_ctx,
 					 child, ctxn, &inherited_all);
 		if (ret)
-			break;
+			goto out_unlock;
 	}
 
 	/*
@@ -10695,7 +10695,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
 		ret = inherit_task_group(event, parent, parent_ctx,
 					 child, ctxn, &inherited_all);
 		if (ret)
-			break;
+			goto out_unlock;
 	}
 
 	raw_spin_lock_irqsave(&parent_ctx->lock, flags);
@@ -10723,6 +10723,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
 	}
 
 	raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
+out_unlock:
 	mutex_unlock(&parent_ctx->mutex);
 
 	perf_unpin_context(parent_ctx);