linux-kernel - [PATCH] tracing: Fix some alloc_event

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Message-ID: <20210824115150.GI31143@kili>
Date:   Tue, 24 Aug 2021 14:51:50 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@...il.com>,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] tracing: Fix some alloc_event_probe() error handling bugs

There are two bugs in this code.  First, if the kzalloc() fails it leads
to a NULL dereference of "ep" on the next line.  Second, if the
alloc_event_probe() function retursn an error then it leads to an
error pointer dereference in the caller.

Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 kernel/trace/trace_eprobe.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index 56a96e9750cf..3044b762cbd7 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -151,7 +151,7 @@ static struct trace_eprobe *alloc_event_probe(const char *group,
 
 	ep = kzalloc(struct_size(ep, tp.args, nargs), GFP_KERNEL);
 	if (!ep) {
-		trace_event_put_ref(ep->event);
+		trace_event_put_ref(event);
 		goto error;
 	}
 	ep->event = event;
@@ -851,7 +851,8 @@ static int __trace_eprobe_create(int argc, const char *argv[])
 		ret = PTR_ERR(ep);
 		/* This must return -ENOMEM, else there is a bug */
 		WARN_ON_ONCE(ret != -ENOMEM);
-		goto error;	/* We know ep is not allocated */
+		ep = NULL;
+		goto error;
 	}
 
 	argc -= 2; argv += 2;
-- 
2.20.1