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    Subject[PATCH AUTOSEL 4.9 14/17] dyndbg: fix a BUG_ON in ddebug_describe_flags
    Date
    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 c7c96bc7654af..91c451e0f4741 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
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