tracing: Fix cmp_entries_dup() to respect sort() comparison rules

commit e63fbd5f6810ed756bbb8a1549c7d4132968baa9 upstream.

The cmp_entries_dup() function used as the comparator for sort()
violated the symmetry and transitivity properties required by the
sorting algorithm. Specifically, it returned 1 whenever memcmp() was
non-zero, which broke the following expectations:

* Symmetry: If x < y, then y > x.
* Transitivity: If x < y and y < z, then x < z.

These violations could lead to incorrect sorting and failure to
correctly identify duplicate elements.

Fix the issue by directly returning the result of memcmp(), which
adheres to the required comparison properties.

Cc: stable@vger.kernel.org
Fixes: 08d43a5fa063 ("tracing: Add lock-free tracing_map")
Link: https://lore.kernel.org/20241203202228.1274403-1-visitorckw@gmail.com
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
index e6cc8d5ab1a459ad7a5727226b104a390a9e90da..3584a35104dd670fb91bc993b2b1210296792d5c 100644 (file)
--- a/kernel/trace/tracing_map.c
+++ b/kernel/trace/tracing_map.c
@@ -845,15 +845,11 @@ int tracing_map_init(struct tracing_map *map)
 static int cmp_entries_dup(const void *A, const void *B)
 {
        const struct tracing_map_sort_entry *a, *b;
-       int ret = 0;
 
        a = *(const struct tracing_map_sort_entry **)A;
        b = *(const struct tracing_map_sort_entry **)B;
 
-       if (memcmp(a->key, b->key, a->elt->map->key_size))
-               ret = 1;
-
-       return ret;
+       return memcmp(a->key, b->key, a->elt->map->key_size);
 }
 
 static int cmp_entries_sum(const void *A, const void *B)