Re: [PATCH] perf hist: fix memory leak if histogram entry is reused

[Jiri Olsa <jolsa@redhat.com>]

On Sat, Feb 23, 2019 at 12:18:18PM +0900, Namhyung Kim wrote:
> Hi,
> 
> On Fri, Feb 22, 2019 at 1:29 AM Jiri Olsa <jolsa@redhat.com> wrote:
> >
> > On Thu, Feb 21, 2019 at 02:53:20PM +0100, Jonas Rabenstein wrote:
> > > On Thu, Feb 21, 2019 at 01:39:09PM +0100, Jiri Olsa wrote:
> > > > On Thu, Feb 21, 2019 at 01:23:06PM +0100, Jonas Rabenstein wrote:
> > > > > In __hists__add_entry the srcline of the addr_location is duplicated
> > > > > for the hist_entry. If hists__findnew_entry returns an already existing
> > > > > hist_entry the srcline has to be freed again as no further reference to
> > > > > that duplicated srcline would exists anymore.
> > > > >
> > > > > Signed-off-by: Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>
> > > > > ---
> > > > >  tools/perf/util/hist.c | 3 +++
> > > > >  1 file changed, 3 insertions(+)
> > > > >
> > > > > diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
> > > > > index 8aad8330e392..25b8dbdbbe87 100644
> > > > > --- a/tools/perf/util/hist.c
> > > > > +++ b/tools/perf/util/hist.c
> > > > > @@ -623,6 +623,9 @@ __hists__add_entry(struct hists *hists,
> > > > >           .ops = ops,
> > > > >   }, *he = hists__findnew_entry(hists, &entry, al, sample_self);
> > > > >
> > > > > + if (he && he->srcline != entry.srcline)
> > > > > +         free(entry.srcline);
> > > > > +
> > > > >   if (!hists->has_callchains && he && he->callchain_size != 0)
> > > > >           hists->has_callchains = true;
> > > > >   return he;
> > > >
> > > > nice, do we have similar issue in here?
> > > >
> > > > jirka
> > > >
> > > >
> > > > ---
> > > > diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
> > > > index 216388003dea..e65e6822c848 100644
> > > > --- a/tools/perf/util/hist.c
> > > > +++ b/tools/perf/util/hist.c
> > > > @@ -966,7 +966,7 @@ iter_add_next_cumulative_entry(struct hist_entry_iter *iter,
> > > >                     .map = al->map,
> > > >                     .sym = al->sym,
> > > >             },
> > > > -           .srcline = al->srcline ? strdup(al->srcline) : NULL,
> > > > +           .srcline = al->srcline,
> > > While this shouldn't leak the memory, we may end up with an al->srcline
> > > to get free afterwards while still having a reference on it within the
> > > hist_entry... Also I could not find where/how the hist_entry is freed up
> > > so we may get an double free if both of al and he clean the srcline.
> > > Of course, with your solution we could spare the useless strdup/free if
> > > we find an hist_entry (which should be the typical case for hotspots..).
> > > Taking a deeper look thus should be beneficial - but I do not have the
> > > time for that right now because I'm still working on the inline-symbol
> > > integration which is more important for me...
> >
> > ok, I'll check it
> 
> I think we can defer calling strdup() to hist_entry__init().

right, thats actualy better fix even for the original patch,
I'll try to post it soon

thanks,
jirka