[iproute PATCH] bpf: Make bytecode-file reading a little more robust

[Phil Sutter]

bpf_parse_string() will now correctly handle:

- Extraneous whitespace,
- OPs on multiple lines and
- overlong file names.

The added feature of allowing to have OPs on multiple lines (like e.g.
tcpdump prints them) is rather a side effect of fixing detection of
malformed bytecode files having random content on a second line, like
e.g.:

| 4,40 0 0 12,21 0 1 2048,6 0 0 262144,6 0 0 0
| foobar

Cc: Daniel Borkmann <dan...@iogearbox.net>
Signed-off-by: Phil Sutter <p...@nwl.cc>
---
 lib/bpf.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/lib/bpf.c b/lib/bpf.c
index e7a4d12fdf2f9..4f52ad4a8f023 100644
--- a/lib/bpf.c
+++ b/lib/bpf.c
@@ -208,11 +208,11 @@ static int bpf_parse_string(char *arg, bool from_file, 
__u16 *bpf_len,
 
        if (from_file) {
                size_t tmp_len, op_len = sizeof("65535 255 255 4294967295,");
-               char *tmp_string, *last;
+               char *tmp_string, *pos, c, c_prev = ' ';
                FILE *fp;
 
                tmp_len = sizeof("4096,") + BPF_MAXINSNS * op_len;
-               tmp_string = calloc(1, tmp_len);
+               tmp_string = pos = calloc(1, tmp_len);
                if (tmp_string == NULL)
                        return -ENOMEM;
 
@@ -223,17 +223,33 @@ static int bpf_parse_string(char *arg, bool from_file, 
__u16 *bpf_len,
                        return -ENOENT;
                }
 
-               if (!fgets(tmp_string, tmp_len, fp)) {
+               while ((c = fgetc(fp)) != EOF) {
+                       switch (c) {
+                       case '\n':
+                               if (c_prev != ',')
+                                       *(pos++) = ',';
+                               break;
+                       case ' ':
+                       case '\t':
+                               if (c_prev != ' ')
+                                       *(pos++) = c;
+                               break;
+                       default:
+                               *(pos++) = c;
+                       }
+                       if (pos - tmp_string == tmp_len)
+                               break;
+                       c_prev = c;
+               }
+
+               if (!feof(fp)) {
                        free(tmp_string);
                        fclose(fp);
-                       return -EIO;
+                       return -E2BIG;
                }
 
                fclose(fp);
-
-               last = &tmp_string[strlen(tmp_string) - 1];
-               if (*last == '\n')
-                       *last = 0;
+               *pos = 0;
 
                *need_release = true;
                *bpf_string = tmp_string;
-- 
2.13.1