tools, bpftool: Fix warning on ignored return value for 'read'

When building bpftool, a warning was introduced by commit a94364603610
("bpftool: Allow to read btf as raw data"), because the return value
from a call to 'read()' is ignored. Let's address it.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191119111706.22440-1-quentin.monnet@netronome.com

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index a7b8bf2..e5bc97b 100644 (file)
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -428,15 +428,15 @@ exit_close:
 static bool is_btf_raw(const char *file)
 {
        __u16 magic = 0;
-       int fd;
+       int fd, nb_read;
 
        fd = open(file, O_RDONLY);
        if (fd < 0)
                return false;
 
-       read(fd, &magic, sizeof(magic));
+       nb_read = read(fd, &magic, sizeof(magic));
        close(fd);
-       return magic == BTF_MAGIC;
+       return nb_read == sizeof(magic) && magic == BTF_MAGIC;
 }
 
 static int do_dump(int argc, char **argv)