diff options
| author | Jeremy Sowden <jeremy@azazel.net> | 2023-03-16 11:07:54 +0000 |
|---|---|---|
| committer | Florian Westphal <fw@strlen.de> | 2023-03-16 23:24:55 +0100 |
| commit | 524ce20b55a2793d380fc1e4b415b1ea5a9512b1 (patch) | |
| tree | 649623c9d659f10b8f30b41b95f46e0b98d5eae1 | |
| parent | 3994535c1d54028ae0a3268e001c9598c7c335ed (diff) | |
pcap: prevent crashes when output `FILE *` is null
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@azazel.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
| -rw-r--r-- | output/pcap/ulogd_output_PCAP.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/output/pcap/ulogd_output_PCAP.c b/output/pcap/ulogd_output_PCAP.c index 0daa2c9..19ce47f 100644 --- a/output/pcap/ulogd_output_PCAP.c +++ b/output/pcap/ulogd_output_PCAP.c @@ -221,14 +221,20 @@ 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 && !write_pcap_header(pi)) { ulogd_log(ULOGD_ERROR, "can't write pcap header: %s\n", @@ -241,12 +247,9 @@ static int append_create_outfile(struct ulogd_pluginstance *upi) 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: |