Format specifier issue when building kernel
Richard Guy Briggs
rgb at redhat.com
Fri Nov 1 16:38:15 UTC 2013
On Fri, Nov 01, 2013 at 12:34:55PM -0400, Steve Grubb wrote:
> On Friday, November 01, 2013 12:24:55 PM Richard Guy Briggs wrote:
> > On Thu, Oct 31, 2013 at 12:25:55PM -0700, William Roberts wrote:
> > > > + if (msg_type != AUDIT_USER_TTY) {
> > > > + char fmt[64];
> > > > + strcat(fmt, " msg='%.");
> > > > + strcat(fmt, "AUDIT_MESSAGE_TEXT_MAX");
> > > > + strcat(fmt, "s'");
> > > > + audit_log_format(ab, fmt, (char *)data);
> > > > + } else {
> > >
> > > I am ok with this. In fact I was going to do this the first time, but I
> > > thought their would be some explicit reason to avoid the additional
> > > run time overhead as the concat could be made at compile time.
> >
> > Ok, this was in danger of starting with fmt in an unknown state. Latest
> > patch:
> >
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > @@ -148,6 +148,8 @@ DEFINE_MUTEX(audit_cmd_mutex);
> > * should be at least that large. */
> > #define AUDIT_BUFSIZ 1024
> >
> > +char usermsg_format[64] = "";
>
> You might want this ^^^ to be static so its not global in scope.
Yup, good point. Thanks.
> -Steve
>
> > /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
> > * audit_freelist. Doing so eliminates many kmalloc/kfree calls. */
> > #define AUDIT_MAXFREE (2*NR_CPUS)
> > @@ -714,11 +716,15 @@ static int audit_receive_msg(struct sk_buff *skb,
> > struct nlmsghdr *nlh) break;
> > }
> > audit_log_common_recv_msg(&ab, msg_type);
> > - if (msg_type != AUDIT_USER_TTY)
> > - audit_log_format(ab,
> > - " msg='%.AUDIT_MESSAGE_TEXT_MAXs'",
> > + if (msg_type != AUDIT_USER_TTY) {
> > + if (unlikely(usermsg_format[0] == 0))
> > + snprintf(usermsg_format,
> > + sizeof(usermsg_format),
> > + " msg=\'%%.%ds\'",
> > + AUDIT_MESSAGE_TEXT_MAX);
> > + audit_log_format(ab, usermsg_format,
> > (char *)data);
> > - else {
> > + } else {
> > int size;
> >
> > audit_log_format(ab, " data=");
> >
> > - RGB
> >
> > --
> > Richard Guy Briggs <rbriggs at redhat.com>
> > Senior Software Engineer
> > Kernel Security
> > AMER ENG Base Operating Systems
> > Remote, Ottawa, Canada
> > Voice: +1.647.777.2635
> > Internal: (81) 32635
> > Alt: +1.613.693.0684x3545
> >
> > --
> > Linux-audit mailing list
> > Linux-audit at redhat.com
> > https://www.redhat.com/mailman/listinfo/linux-audit
>
- RGB
--
Richard Guy Briggs <rbriggs at redhat.com>
Senior Software Engineer
Kernel Security
AMER ENG Base Operating Systems
Remote, Ottawa, Canada
Voice: +1.647.777.2635
Internal: (81) 32635
Alt: +1.613.693.0684x3545
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