Commit d9815bff authored Mar 06, 2020 by Artem Savkov Committed by Steven Rostedt (VMware) Mar 11, 2020

ftrace: Return the first found result in lookup_rec()

It appears that ip ranges can overlap so. In that case lookup_rec()
returns whatever results it got last even if it found nothing in last
searched page.

This breaks an obscure livepatch late module patching usecase:
  - load livepatch
  - load the patched module
  - unload livepatch
  - try to load livepatch again

To fix this return from lookup_rec() as soon as it found the record
containing searched-for ip. This used to be this way prior lookup_rec()
introduction.

Link: http://lkml.kernel.org/r/20200306174317.21699-1-asavkov@redhat.com



Cc: stable@vger.kernel.org
Fixes: 7e16f581 ("ftrace: Separate out functionality from ftrace_location_range()")
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent 2910b5aa

kernel/trace/ftrace.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1547,6 +1547,8 @@ static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end)
		rec = bsearch(&key, pg->records, pg->index,
		sizeof(struct dyn_ftrace),
		ftrace_cmp_recs);
		if (rec)
		break;
		}
		return rec;
		}

Admin message