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    Subject[PATCH AUTOSEL 4.14 02/35] samples, bpf: fix to change the buffer size for read()
    Date
    From: Chang-Hsien Tsai <luke.tw@gmail.com>

    [ Upstream commit f7c2d64bac1be2ff32f8e4f500c6e5429c1003e0 ]

    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 <luke.tw@gmail.com>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 2325d7ad76df..e8e8b756dc52 100644
    --- a/samples/bpf/bpf_load.c
    +++ b/samples/bpf/bpf_load.c
    @@ -613,7 +613,7 @@ 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);
    --
    2.20.1
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