[PATCH 4.19 051/168] dyndbg: fix a BUG_ON in ddebug_describe_flags

Greg Kroah-Hartman
2020-08-17T17:49:39Z

From: Jim Cromie <jim.cromie@gmail.com>

[ 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>
---
lib/dynamic_debug.c | 23 +++++++++++------------
1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index dbf2b457e47e6..9305ff43fc155 100644
--- 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");

--
2.25.1