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Subject[GIT PULL] ftrace: Return the first found result in lookup_rec()


Have ftrace lookup_rec() return a consistent record otherwise it
can break live patching.

Please pull the latest trace-v5.6-rc4 tree, which can be found at:


Tag SHA1: 3bedd0c3802cdffacf9fd6a4cac9f3fa6a4da477
Head SHA1: d9815bff6b379ff46981bea9dfeb146081eab314

Artem Savkov (1):
ftrace: Return the first found result in lookup_rec()

kernel/trace/ftrace.c | 2 ++
1 file changed, 2 insertions(+)
commit d9815bff6b379ff46981bea9dfeb146081eab314
Author: Artem Savkov <>
Date: Fri Mar 6 18:43:17 2020 +0100

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()


Fixes: 7e16f581a817 ("ftrace: Separate out functionality from ftrace_location_range()")
Signed-off-by: Artem Savkov <>
Signed-off-by: Steven Rostedt (VMware) <>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 3f7ee102868a..fd81c7de77a7 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -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),
+ if (rec)
+ break;
return rec;
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