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| author | Kuan-Wei Chiu <visitorckw@gmail.com> | 2024-12-09 21:42:26 +0800 |
|---|---|---|
| committer | Namhyung Kim <namhyung@kernel.org> | 2024-12-09 13:54:08 -0800 |
| commit | 246dfe3dc199246bd64635163115f2691623fc53 (patch) | |
| tree | 5bd0f5e4f408a698a01bab442b4bcc35538c7cac /tools/perf | |
| parent | c33aea446bf555ab2b4e06deb914ba8f87cdb068 (diff) | |
| download | lwn-246dfe3dc199246bd64635163115f2691623fc53.tar.gz lwn-246dfe3dc199246bd64635163115f2691623fc53.zip | |
perf ftrace: Fix undefined behavior in cmp_profile_data()
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>
Diffstat (limited to 'tools/perf')
| -rw-r--r-- | tools/perf/builtin-ftrace.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c index 272d3c70810e..a56cf8b0a7d4 100644 --- a/tools/perf/builtin-ftrace.c +++ b/tools/perf/builtin-ftrace.c @@ -1151,8 +1151,9 @@ static int cmp_profile_data(const void *a, const void *b) if (v1 > v2) return -1; - else + if (v1 < v2) return 1; + return 0; } static void print_profile_result(struct perf_ftrace *ftrace) |