[PATCH v2 2/4] perf: Fix uninitialized bitfields in perf_clear_branch_entry_bitfields()

[Puranjay Mohan]

perf_clear_branch_entry_bitfields() zeroes individual bitfields of struct
perf_branch_entry but misses the new_type (4 bits) and priv (3 bits)
fields. This means any code path that relies on this function to produce
a clean entry may expose stale or uninitialised data in these fields to
userspace.

The function was introduced by commit bfe4daf850f4 ("perf/core: Add
perf_clear_branch_entry_bitfields() helper") specifically to "centralize
the initialization to avoid missing a field in case more are added."
Unfortunately, the commits that later added new_type and priv to struct
perf_branch_entry only updated the UAPI header and did not update this
clearing function.

Zero new_type and priv alongside the other bitfields.

Fixes: b190bc4ac9e6 ("perf: Extend branch type classification")
Fixes: 5402d25aa571 ("perf: Capture branch privilege information")
Signed-off-by: Puranjay Mohan <puranjay at kernel.org>
---
 include/linux/perf_event.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 48d851fbd8ea..d7f39b7e9cda 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1481,6 +1481,8 @@ static inline void perf_clear_branch_entry_bitfields(struct perf_branch_entry *b
 	br->cycles	= 0;
 	br->type	= 0;
 	br->spec	= PERF_BR_SPEC_NA;
+	br->new_type	= 0;
+	br->priv	= 0;
 	br->reserved	= 0;
 }
 
-- 
2.52.0