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The comparison function cmp_profile_data() violates the C standard's requirements for qsort() comparison functions, which mandate symmetry and transitivity: * Symmetry: If x < y, then y > x. * Transitivity: If x < y and y < z, then x < z. When v1 and v2 are equal, the function incorrectly returns 1, breaking symmetry and transitivity. This causes undefined behavior, which can lead to memory corruption in certain versions of glibc [1]. Fix the issue by returning 0 when v1 and v2 are equal, ensuring compliance with the C standard and preventing undefined behavior. Link: https://www.qualys.com/2024/01/30/qsort.txt [1] Fixes: 0f223813edd0 ("perf ftrace: Add 'profile' command") Fixes: 74ae366c37b7 ("perf ftrace profile: Add -s/--sort option") Cc: stable@vger.kernel.org Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com> Reviewed-by: Namhyung Kim <namhyung@kernel.org> Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: jserv@ccns.ncku.edu.tw Cc: chuang@cs.nycu.edu.tw Link: https://lore.kernel.org/r/20241209134226.1939163-1-visitorckw@gmail.com Signed-off-by: Namhyung Kim <namhyung@kernel.org>