[tip:perf/core] perf_events: Fix invalid pointer when pid is invalid

[tip-bot for Stephane Eranian <eranian@google.com>]

Commit-ID:  540804b5c52065a87d826f7714b18a3ec0b269f9
Gitweb:     http://git.kernel.org/tip/540804b5c52065a87d826f7714b18a3ec0b269f9
Author:     Stephane Eranian <eranian@google.com>
AuthorDate: Mon, 4 Oct 2010 12:00:02 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 4 Oct 2010 12:47:20 +0200

perf_events: Fix invalid pointer when pid is invalid

This patch fixes an error in perf_event_open() when the pid
provided by the user is invalid. find_lively_task_by_vpid()
does not return NULL on error but an error code. Without the
fix the error code was silently passed to find_get_context()
which would eventually cause a invalid pointer dereference.

Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: paulus@samba.org
Cc: davem@davemloft.net
Cc: fweisbec@gmail.com
Cc: perfmon2-devel@lists.sf.net
Cc: eranian@gmail.com
Cc: robert.richter@amd.com
LKML-Reference: <4ca9a5d1.e8e9d80a.3dbb.ffff8f2e@mx.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/perf_event.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index c16158c..64507ea 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -5616,8 +5616,13 @@ SYSCALL_DEFINE5(perf_event_open,
 		}
 	}
 
-	if (pid != -1)
+	if (pid != -1) {
 		task = find_lively_task_by_vpid(pid);
+		if (IS_ERR(task)) {
+			err = PTR_ERR(task);
+			goto err_group_fd;
+		}
+	}
 
 	/*
 	 * Get the target context (task or percpu):