If ulogd2 receives a signal it will attempt to re-open the pcap output file. If this fails (because the permissions or ownership have changed for example), the FILE pointer will be null and when the next packet comes in, the null pointer will be passed to fwrite and ulogd will crash. Instead, assign the return value of `fopen` to a local variable, and only close the existing stream if `fopen` succeeded. Link: https://bugs.launchpad.net/ubuntu/+source/ulogd2/+bug/1429778 Signed-off-by: Jeremy Sowden <jeremy@xxxxxxxxxx> --- output/pcap/ulogd_output_PCAP.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/output/pcap/ulogd_output_PCAP.c b/output/pcap/ulogd_output_PCAP.c index 220fc6dec5fe..0bb1f32b53ed 100644 --- a/output/pcap/ulogd_output_PCAP.c +++ b/output/pcap/ulogd_output_PCAP.c @@ -221,14 +221,18 @@ static int append_create_outfile(struct ulogd_pluginstance *upi) struct pcap_instance *pi = (struct pcap_instance *) &upi->private; char *filename = upi->config_kset->ces[0].u.string; struct stat st_of; + FILE *of; - pi->of = fopen(filename, "a"); - if (!pi->of) { + of = fopen(filename, "a"); + if (!of) { ulogd_log(ULOGD_ERROR, "can't open pcap file %s: %s\n", filename, strerror(errno)); return -EPERM; } + if (pi->of) + fclose(pi->of); + pi->of = of; if (fstat(fileno(pi->of), &st_of) == 0 && st_of.st_size == 0) { if (!write_pcap_header(pi)) { ulogd_log(ULOGD_ERROR, "can't write pcap header: %s\n", @@ -236,18 +240,14 @@ static int append_create_outfile(struct ulogd_pluginstance *upi) return -ENOSPC; } } - return 0; } static void signal_pcap(struct ulogd_pluginstance *upi, int signal) { - struct pcap_instance *pi = (struct pcap_instance *) &upi->private; - switch (signal) { case SIGHUP: ulogd_log(ULOGD_NOTICE, "reopening capture file\n"); - fclose(pi->of); append_create_outfile(upi); break; default: -- 2.39.2
