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 --- tools/perf/builtin-ftrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
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)
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
Thanks for the fix. Namhyung
tools/perf/builtin-ftrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
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)
2.34.1
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
- Arnaldo
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
On Mon, 09 Dec 2024 21:42:26 +0800, Kuan-Wei Chiu 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.
[...]
Applied to perf-tools, thanks!
Best regards, Namhyung
linux-stable-mirror@lists.linaro.org
-
Arnaldo Carvalho de Melo -
Kuan-Wei Chiu -
Namhyung Kim