diff options
| -rw-r--r-- | pcap-linux.c | 39 |
1 files changed, 38 insertions, 1 deletions
diff --git a/pcap-linux.c b/pcap-linux.c index 6e1d89b6..546d0369 100644 --- a/pcap-linux.c +++ b/pcap-linux.c @@ -3890,9 +3890,46 @@ static int pcap_wait_for_frames_mmap(pcap_t *handle) * Now check the event device. */ if (pollinfo[1].revents & POLLIN) { + ssize_t nread; uint64_t value; - (void)read(handlep->poll_breakloop_fd, &value, + + /* + * This should never fail, but, just + * in case.... + */ + nread = read(handlep->poll_breakloop_fd, &value, sizeof(value)); + if (nread == -1) { + pcap_fmt_errmsg_for_errno(handle->errbuf, + PCAP_ERRBUF_SIZE, + errno, + "Error reading from event FD"); + return PCAP_ERROR; + } + + /* + * According to the Linux read(2) man + * page, read() will transfer at most + * 2^31-1 bytes, so the return value is + * either -1 or a value between 0 + * and 2^31-1, so it's non-negative. + * + * Cast it to size_t to squelch + * warnings from the compiler; add this + * comment to squelch warnings from + * humans reading the code. :-) + * + * Don't treat an EOF as an error, but + * *do* treat a short read as an error; + * that "shouldn't happen", but.... + */ + if (nread != 0 && + (size_t)nread < sizeof(value)) { + snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, + "Short read from event FD: expected %zu, got %zd", + sizeof(value), nread); + return PCAP_ERROR; + } /* * This event gets signaled by a |