From: Chang-Hsien Tsai
> Sent: 19 May 2019 10:06
> If the trace for read is larger than 4096,
> the return value sz will be 4096.
> This results in off-by-one error on buf.
>
> static char buf[4096];
> ssize_t sz;
>
> sz = read(trace_fd, buf, sizeof(buf));
> if (sz > 0) {
> buf[sz] = 0;
> puts(buf);
> }
>
> Signed-off-by: Chang-Hsien Tsai <[email protected]>
> ---
> samples/bpf/bpf_load.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
> index eae7b635343d..d4da90070b58 100644
> --- a/samples/bpf/bpf_load.c
> +++ b/samples/bpf/bpf_load.c
> @@ -678,7 +678,7 @@ void read_trace_pipe(void)
> static char buf[4096];
> ssize_t sz;
>
> - sz = read(trace_fd, buf, sizeof(buf));
> + sz = read(trace_fd, buf, sizeof(buf)-1);
> if (sz > 0) {
> buf[sz] = 0;
> puts(buf);
Why not change the puts() to fwrite(buf, sz, 1, stdout) ?
Then you don't need the '\0' terminator.
David
-
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