perf annotate: Avoid TUI crash when navigating in the annotation of recursive functions

In 'perf report', entering a recursive function from inside of itself
(either directly of indirectly through some other function) results in
calling symbol__annotate2 multiple() times, and freeing the whole
disassembly when exiting from the innermost instance.

The first issue causes the function's disassembly to be duplicated, and
the latter a heap use-after-free (and crash) when trying to access the
disassembly again.

I reproduced the bug on perf 5.11.22 (Ubuntu 20.04.3 LTS) and 5.16.rc8
with the following testcase (compile with gcc recursive.c -o recursive).
To reproduce:

- perf record ./recursive
- perf report
- enter fibonacci and annotate it
- move the cursor on one of the "callq fibonacci" instructions and press enter
- at this point there will be two copies of the function in the disassembly
- go back by pressing q, and perf will crash

#include <stdio.h>

int fibonacci(int n)
{
if(n <= 2) return 1;
return fibonacci(n-1) + fibonacci(n-2);
}

int main()
{
printf("%d\n", fibonacci(40));
}

This patch addresses the issue by annotating a function and freeing the
associated memory on exit only if no annotation is already present, so
that a recursive function is only annotated on entry.

Signed-off-by: Dario Petrillo <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: [e-mail]
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/ui/browsers/annotate.c

···
 		.opts = opts,
 	};
 	int ret = -1, err;
+	int not_annotated = list_empty(&notes->src->source);
 
 	if (sym == NULL)
 		return -1;
···
 	if (ms->map->dso->annotate_warned)
 		return -1;
 
-	err = symbol__annotate2(ms, evsel, opts, &browser.arch);
-	if (err) {
-		char msg[BUFSIZ];
-		ms->map->dso->annotate_warned = true;
-		symbol__strerror_disassemble(ms, err, msg, sizeof(msg));
-		ui__error("Couldn't annotate %s:\n%s", sym->name, msg);
-		goto out_free_offsets;
+	if (not_annotated) {
+		err = symbol__annotate2(ms, evsel, opts, &browser.arch);
+		if (err) {
+			char msg[BUFSIZ];
+			ms->map->dso->annotate_warned = true;
+			symbol__strerror_disassemble(ms, err, msg, sizeof(msg));
+			ui__error("Couldn't annotate %s:\n%s", sym->name, msg);
+			goto out_free_offsets;
+		}
 	}
 
 	ui_helpline__push("Press ESC to exit");
···
 
 	ret = annotate_browser__run(&browser, evsel, hbt);
 
-	annotated_source__purge(notes->src);
+	if(not_annotated)
+		annotated_source__purge(notes->src);
 
 out_free_offsets:
-	zfree(&notes->offsets);
+	if(not_annotated)
+		zfree(&notes->offsets);
 	return ret;
 }