From: Natalia Petrova <n.petrova@fintech.ru>
Date: Wed, 11 Jan 2023 15:04:09 +0300
Subject: trace_events_hist: add check for return value of 'create_hist_field'
Git-commit: 8b152e9150d07a885f95e1fd401fc81af202d9a4
Patch-mainline: v6.2-rc6
References: git-fixes

Function 'create_hist_field' is called recursively at
trace_events_hist.c:1954 and can return NULL-value that's why we have
to check it to avoid null pointer dereference.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Link: https://lkml.kernel.org/r/20230111120409.4111-1-n.petrova@fintech.ru

Cc: stable@vger.kernel.org
Fixes: 30350d65ac56 ("tracing: Add variable support to hist triggers")
Signed-off-by: Natalia Petrova <n.petrova@fintech.ru>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Petr Pavlu <petr.pavlu@suse.com>
---
 kernel/trace/trace_events_hist.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index fcaf226b7744..5edbf6b1da3f 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1988,6 +1988,8 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 		unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
 		hist_field->fn = hist_field_log2;
 		hist_field->operands[0] = create_hist_field(hist_data, field, fl, NULL);
+		if (!hist_field->operands[0])
+			goto free;
 		hist_field->size = hist_field->operands[0]->size;
 		hist_field->type = kstrdup(hist_field->operands[0]->type, GFP_KERNEL);
 		if (!hist_field->type)