samples, bpf: fix to change the buffer size for read()
authorChang-Hsien Tsai <luke.tw@gmail.com>
Sun, 19 May 2019 09:05:44 +0000 (09:05 +0000)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sun, 21 Jul 2019 07:04:17 +0000 (09:04 +0200)
[ 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

index 2325d7ad76df83764293cd5b74e473f8cc85426b..e8e8b756dc52c0842fdd07e088705ac3135d4e2b 100644 (file)
@@ -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);