On Mon, Dec 9, 2024 at 12:26 PM Arnaldo Carvalho de Melo acme@kernel.org wrote:
On Mon, Dec 09, 2024 at 09:02:24AM -0800, Namhyung Kim wrote:
Hello,
On Mon, Dec 9, 2024 at 5:42 AM Kuan-Wei Chiu visitorckw@gmail.com wrote:
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
I'm assuming you'll pick this for perf-tools, ok?
Reviewed-by: Arnaldo Carvalho de Melo acme@redhat.com
Yep, sure.
Thanks, Namhyung