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From:   "Enrico Weigelt, metux IT consult" <info@metux.net>
To:     linux-kernel@vger.kernel.org
Cc:     pmladek@suse.com, rostedt@goodmis.org,
        sergey.senozhatsky@gmail.com, andriy.shevchenko@linux.intel.com,
        linux@rasmusvillemoes.dk, kafai@fb.com, songliubraving@fb.com,
        yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org,
        netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: [PATCH] lib: vsprintf: check for NULL device_node name in device_node_string()
Date:   Wed, 17 Feb 2021 13:15:43 +0100
Message-Id: <20210217121543.13010-1-info@metux.net>
Precedence: bulk

Under rare circumstances it may happen that a device node's name is NULL
(most likely kernel bug in some other place). In such situations anything
but helpful, if the debug printout crashes, and nobody knows what actually
happened here.

Therefore protect it by an explicit NULL check and print out an extra
warning.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
---
 lib/vsprintf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3b53c73580c5..050a60b88073 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2013,6 +2013,10 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
 			break;
 		case 'n':	/* name */
 			p = fwnode_get_name(of_fwnode_handle(dn));
+			if (!p) {
+				pr_warn("device_node without name. Kernel bug ?\n");
+				p = "<NULL>";
+			}
 			precision = str_spec.precision;
 			str_spec.precision = strchrnul(p, '@') - p;
 			buf = string(buf, end, p, str_spec);
-- 
2.11.0