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>

1 files changed, 6 insertions, 1 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index c16158c77dfd..64507eaa2d9e 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):