linux-kernel - [PATCH 07/16] dyndbg: fix a BUG_ON in ddebug

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Date:   Tue, 29 Oct 2019 14:00:39 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     jbaron@...mai.com, linux-kernel@...r.kernel.org
Cc:     linux@...musvillemoes.dk, greg@...ah.com,
        Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH 07/16] dyndbg: fix a BUG_ON in ddebug_change

banish a BUG_ON(stringbuf-too-short) by sticking a fixed-size one
inside a struct, and passing &it around instead of the string & size.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/dynamic_debug.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 4ce0c53cdcfd..3ac77c49d623 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -60,6 +60,8 @@ struct ddebug_iter {
 	unsigned int idx;
 };
 
+struct flagsbuf { char buf[10]; };
+
 static DEFINE_MUTEX(ddebug_lock);
 static LIST_HEAD(ddebug_tables);
 static int verbose;
@@ -75,21 +77,19 @@ static struct { unsigned flag:8; char opt_char; } opt_array[] = {
 };
 
 /* format a string into buf[] which describes the _ddebug's flags */
-static char *ddebug_describe_flags(struct _ddebug *dp, char *buf,
-				    size_t maxlen)
+static char *ddebug_describe_flags(struct _ddebug *dp, struct flagsbuf *flags)
 {
-	char *p = buf;
+	char *p = flags->buf;
 	int i;
 
-	BUG_ON(maxlen < 6);
 	for (i = 0; i < ARRAY_SIZE(opt_array); ++i)
 		if (dp->flags & opt_array[i].flag)
 			*p++ = opt_array[i].opt_char;
-	if (p == buf)
+	if (p == flags->buf)
 		*p++ = '_';
 	*p = '\0';
 
-	return buf;
+	return flags->buf;
 }
 
 #define vnpr_info(lvl, fmt, ...)				\
@@ -135,7 +135,7 @@ static int ddebug_change(const struct ddebug_query *query,
 	struct ddebug_table *dt;
 	unsigned int newflags;
 	unsigned int nfound = 0;
-	char flagbuf[10];
+	struct flagsbuf flagbuf;
 
 	/* search for matching ddebugs */
 	mutex_lock(&ddebug_lock);
@@ -190,8 +190,7 @@ static int ddebug_change(const struct ddebug_query *query,
 			vpr_info("changed %s:%d [%s]%s =%s\n",
 				 dp->filename, dp->lineno,
 				 dt->mod_name, dp->function,
-				 ddebug_describe_flags(dp, flagbuf,
-						       sizeof(flagbuf)));
+				 ddebug_describe_flags(dp, &flagbuf));
 		}
 	}
 	mutex_unlock(&ddebug_lock);
@@ -804,7 +803,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
 {
 	struct ddebug_iter *iter = m->private;
 	struct _ddebug *dp = p;
-	char flagsbuf[10];
+	struct flagsbuf flagbuf;
 
 	v9pr_info("called m=%p p=%p\n", m, p);
 
@@ -817,7 +816,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
 	seq_printf(m, "%s:%u [%s]%s =%s \"",
 		   dp->filename, dp->lineno,
 		   iter->table->mod_name, dp->function,
-		   ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
+		   ddebug_describe_flags(dp, &flagbuf));
 	seq_escape(m, dp->format, "\t\r\n\"");
 	seq_puts(m, "\"\n");
 
-- 
2.21.0