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SubjectRe: [PATCH 1/3] Fix backward-ring-buffer.c format-truncation error
Em Wed, Jul 24, 2019 at 11:45:10AM -0700, Numfor Mbiziwo-Tiapo escreveu:
> Perf does not build with the ubsan (undefined behavior sanitizer)
> and there is an error that says:
>
> tests/backward-ring-buffer.c:23:45: error: ‘%d’ directive output
> may be truncated writing between 1 and 10 bytes into a region of
> size 8 [-Werror=format-truncation=]
> snprintf(proc_name, sizeof(proc_name), "p:%d\n", i);
>
> This can be reproduced by running (from the tip directory):
> make -C tools/perf USE_CLANG=1 EXTRA_CFLAGS="-fsanitize=undefined"
>
> Th error occurs because they are writing to the 10 byte buffer - the
> index 'i' of the for loop and the 2 byte hardcoded string. If somehow 'i'
> was greater than 8 bytes (10 - 2), then the snprintf function would
> truncate the string. Increasing the size of the buffer fixes the error.
>
> Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com>
> ---
> tools/perf/tests/backward-ring-buffer.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/tests/backward-ring-buffer.c b/tools/perf/tests/backward-ring-buffer.c
> index 6d598cc071ae..1a9c3becf5ff 100644
> --- a/tools/perf/tests/backward-ring-buffer.c
> +++ b/tools/perf/tests/backward-ring-buffer.c
> @@ -18,7 +18,7 @@ static void testcase(void)
> int i;
>
> for (i = 0; i < NR_ITERS; i++) {
> - char proc_name[10];
> + char proc_name[15];
>
> snprintf(proc_name, sizeof(proc_name), "p:%d\n", i);
> prctl(PR_SET_NAME, proc_name);

This was fixed already by:

commit 11c1ea6f1a9bc97bf857fd12f72eacb6c69794e2
Author: Changbin Du <changbin.du@gmail.com>
Date: Sat Mar 16 16:05:43 2019 +0800

perf tools: Fix errors under optimization level '-Og'

Optimization level '-Og' offers a reasonable level of optimization while
maintaining fast compilation and a good debugging experience. This patch
tries to make it work.

$ make DEBUG=1 EXTRA_CFLAGS='-Og'
bench/epoll-ctl.c: In function ‘do_threads’:
bench/epoll-ctl.c:274:9: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
return ret;
^~~
...

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>

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