From f79e36fa599d6fa128c2cb7fa1e916bf0cf335bd Mon Sep 17 00:00:00 2001 From: Kuan-Wei Chiu Date: Wed, 12 Mar 2025 22:51:00 +0900 Subject: [PATCH] tracing: Fix cmp_entries_dup() to respect sort() comparison rules BugLink: https://bugs.launchpad.net/bugs/2102118 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 Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman Signed-off-by: Koichiro Den Signed-off-by: Stefan Bader --- kernel/trace/tracing_map.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c index 3a56e7c8aa4f..1921ade45be3 100644 --- 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)