Re: [PATCH v3] audit: log AUDIT_TIME_* records only from rules

On Thu, Feb 10, 2022 at 6:46 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > On 2022-01-31 20:29, Paul Moore wrote: > > On Mon, Jan 31, 2022 at 6:29 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > On 2022-01-31 17:02, Paul Moore wrote: > > > > On Wed, Jan 26, 2022 at 8:52 AM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > > > On 2022-01-25 22:24, Richard Guy Briggs wrote: This isn't as complete of a response as I would like, but I wanted to get *something* back to you same-day since the delays are getting a bit long ... > > > > [WARNING: not compiled, tested, yadda yadda] > > > > > > > > void audit_log_time(struct audit_context ctx, struct audit_buffer **abp) > > > > { > > > > int i; > > > > int type = ctx->type; > > > > struct audit_buffer *ab = *abp; > > > > struct audit_ntp_val *ntp; > > > > const struct timespec64 *tk; > > > > const char *ntp_name[] = { > > > > "offset", > > > > "freq", > > > > "status", > > > > "tai", > > > > "tick", > > > > "adjust", > > > > }; > > > > > > > > do { > > > > if (type == AUDIT_TIME_ADJNTPVAL) { > > > > ntp = ctx->time.ntp_data.val; > > > > for (i = 0; i < AUDIT_NTP_NVALS; i++) { > > > > if (ntp[i].newval != ntp[i].oldval) { > > > > audit_log_format(ab, > > > > "op=%s old=%lli new=%lli", > > > > ntp_name[type], > > > > ntp[i].oldval, ntp[i].newval); > > > > } > > > > } > > > > } else { > > > > tk = &ctx->time.tk_injoffset; > > > > audit_log_format(ab, "sec=%lli nsec=%li", > > > > (long long)tk->tv_sec, tk->tv_nsec); > > > > } > > > > audit_log_end(ab); > > > > > > There is an audit_log_end() in the calling function, show_special(), so > > > it should only be called here if there is another buffer allocated in > > > this function after it. audit_log_end() is protected should it be > > > called with no valid buffer so this wouldn't create a bug. > > > > As audit_log_end() can safely take a NULL audit_buffer I don't care if we > > send it back a valid buffer or a NULL. IMO it happens to be easier (and > > cleaner) to send back a NULL. > > None of the other callees in show_special() do that, so this would be > surprising behaviour that could cause a future bug ... To be both honest and frank: I disagree with your assessment. If you really want to be concerned about this, there are plenty of ways to mitigate the "risk" depending on your comfort level; comments and returning within the switch/case block are just some of the options. > > > > if (*abp) { > > > > *abp = NULL; > > > > type = (type == AUDIT_TIME_ADJNTPVAL ? > > > > AUDIT_TIME_INJOFFSET : AUDIT_TIME_ADJNTPVAL); > > > > > > This cannot be allocated if there are no more needed above ... > > > > My mistake, I was distracted a few times while typing up my reply and the > > code within; while I had that detail in mind when I started I lost it > > during one of the interruptions. As penance, I wrote up some slightly more > > proper code and at least made sure it complied, although I've not tried > > booting it ... > > Did you test the code I submitted? It compiles and works. I found this > code harder to follow. This was partly why I wanted to leave one of the > record types outside of show_special() but I did find a way to > accomodate both with a minimum of overhead. Once again, I disagree with your assessment of the code. I'm not sure how to put this politely, but I personally found your audit_log_time() implementation to be awkward; the AUDIT_TIME_INJOFFSET goto/jump to "tk" at the top of the function was not something I'm going to merge. You don't have to like my suggestion, but please send me a patch that has a somewhat reasonable code flow. I know you often want, or at least ask for explicit suggestions (hence my untested code example), but since you didn't like that let me just say this: when in doubt, limit your use of gotos/jumps to error handling unless there is something significantly unusual about the function. In my opinion there is nothing significantly unusual about the audit_log_time() function to require a jump as you've currently done.

paul-moore.com