From: Tymoteusz Blazejczyk <tymoteusz.blazejczyk@intel.com>
Date: Wed, 12 Jun 2019 08:30:32 +0000 (+0200)
Subject: Fixed the fread call in the savefile.c file
X-Git-Tag: libpcap-1.10-bp~483^2~1
X-Git-Url: https://git.tcpdump.org/libpcap/commitdiff_plain/9157a663d9e845e23697f598994f53f67cfef799

Fixed the fread call in the savefile.c file

Currently it was an undefined behavior (UB).
It passes wrong parameters to the fread function call (1 byte, 4 elements).
It should be 4 bytes and 1 element because the `magic` variable is a single 32-bits integer (4 bytes).

```
bytes_read = fread(pointer, number_of_bytes, number_of_elements, file);
```

On some machines the `fread()` call returned 0 with no error from the `ferror()` call with
correct and valid PCAP files.

Reference: https://en.cppreference.com/w/c/io/fread
---

diff --git a/savefile.c b/savefile.c
index 152c9177..e6404e74 100644
--- a/savefile.c
+++ b/savefile.c
@@ -359,7 +359,7 @@ pcap_fopen_offline_with_tstamp_precision(FILE *fp, u_int precision,
 	 * Windows Sniffer, and Microsoft Network Monitor) all have magic
 	 * numbers that are unique in their first 4 bytes.
 	 */
-	amt_read = fread((char *)&magic, 1, sizeof(magic), fp);
+	amt_read = fread(&magic, sizeof(magic), 1, fp);
 	if (amt_read != sizeof(magic)) {
 		if (ferror(fp)) {
 			pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,