dyndbg: fix a BUG_ON in ddebug_describe_flags

[ Upstream commit f678ce8cc3cb2ad29df75d8824c74f36398ba871 ]

ddebug_describe_flags() currently fills a caller provided string buffer,
after testing its size (also passed) in a BUG_ON.  Fix this by
replacing them with a known-big-enough string buffer wrapped in a
struct, and passing that instead.

Also simplify ddebug_describe_flags() flags parameter from a struct to
a member in that struct, and hoist the member deref up to the caller.
This makes the function reusable (soon) where flags are unpacked.

Acked-by: <jbaron@akamai.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20200719231058.1586423-8-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index c7c96bc7654af7c4d5f3c8bbf595989f9b3d0ebf..91c451e0f4741aaf97d272b96891a21e28047353 100644 (file)
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -85,22 +85,22 @@ static struct { unsigned flag:8; char opt_char; } opt_array[] = {
        { _DPRINTK_FLAGS_NONE, '_' },
 };
 
+struct flagsbuf { char buf[ARRAY_SIZE(opt_array)+1]; };
+
 /* 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(unsigned int flags, struct flagsbuf *fb)
 {
-       char *p = buf;
+       char *p = fb->buf;
        int i;
 
-       BUG_ON(maxlen < 6);
        for (i = 0; i < ARRAY_SIZE(opt_array); ++i)
-               if (dp->flags & opt_array[i].flag)
+               if (flags & opt_array[i].flag)
                        *p++ = opt_array[i].opt_char;
-       if (p == buf)
+       if (p == fb->buf)
                *p++ = '_';
        *p = '\0';
 
-       return buf;
+       return fb->buf;
 }
 
 #define vpr_info(fmt, ...)                                     \
@@ -142,7 +142,7 @@ 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 fbuf;
 
        /* search for matching ddebugs */
        mutex_lock(&ddebug_lock);
@@ -199,8 +199,7 @@ static int ddebug_change(const struct ddebug_query *query,
                        vpr_info("changed %s:%d [%s]%s =%s\n",
                                 trim_prefix(dp->filename), dp->lineno,
                                 dt->mod_name, dp->function,
-                                ddebug_describe_flags(dp, flagbuf,
-                                                      sizeof(flagbuf)));
+                                ddebug_describe_flags(dp->flags, &fbuf));
                }
        }
        mutex_unlock(&ddebug_lock);
@@ -779,7 +778,7 @@ 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 flags;
 
        vpr_info("called m=%p p=%p\n", m, p);
 
@@ -792,7 +791,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
        seq_printf(m, "%s:%u [%s]%s =%s \"",
                   trim_prefix(dp->filename), dp->lineno,
                   iter->table->mod_name, dp->function,
-                  ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
+                  ddebug_describe_flags(dp->flags, &flags));
        seq_escape(m, dp->format, "\t\r\n\"");
        seq_puts(m, "\"\n");