Created attachment 205325 [details]
crash sample

Background: With some spare time, I randomly decided to apply AFL to `usbdump -r <file>`. To get it going, I used a seed file of 10240 bytes from /dev/random and additionally augmented the source to avoid the magic value check and the major/minor checks that one sees in usbdump.c:init_rfile(struct usbcap *). With those changes, AFL under VMWare will find this crash in seconds. From the quick diagnosis, it seems to be a bad memory access and the following is based on June 24 2019 usbdump.c from CURRENT copied into a 12.O-RELEASE tree and built (so one is aware) and print_packets() looking to be the culprit:

[arr@gunther ~]$ gdb /usr/obj/usr/src/amd64.amd64/usr.sbin/usbdump/usbdump.full
GNU gdb (GDB) 8.2.1 [GDB v8.2.1 for FreeBSD]
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-portbld-freebsd12.0".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/obj/usr/src/amd64.amd64/usr.sbin/usbdump/usbdump.full...done.
(gdb) r -r usbdump_read_sample
Starting program: /usr/obj/usr/src/amd64.amd64/usr.sbin/usbdump/usbdump.full -r usbdump_read_sample

Program received signal SIGBUS, Bus error.
strlen (str=0x180011000000e2 <error: Cannot access memory at address 0x180011000000e2>) at /usr/src/lib/libc/string/strlen.c:101
101    		va = (*lp - mask01);
(gdb) bt
#0  strlen (str=0x180011000000e2 <error: Cannot access memory at address 0x180011000000e2>) at /usr/src/lib/libc/string/strlen.c:101
#1  0x0000000800397539 in __vfprintf (fp=<optimized out>, locale=0x8004084e8 <__xlocale_global_locale>, fmt0=<optimized out>,
    ap=<optimized out>) at /usr/src/lib/libc/stdio/vfprintf.c:854
#2  0x0000000800395144 in vfprintf_l (fp=0x8004098e8, locale=0x8004084e8 <__xlocale_global_locale>,
    fmt0=0x200b12 "%.*s.%06ld usbus%d.%d %s-%s-EP=%08x,SPD=%s,NFR=%d,SLEN=%d,IVAL=%d%s%s\n", ap=0x7fffffffe720)
    at /usr/src/lib/libc/stdio/vfprintf.c:285
#3  0x00000008003e21c4 in printf (fmt=0x1 <error: Cannot access memory at address 0x1>) at /usr/src/lib/libc/stdio/printf.c:57
#4  0x0000000000203432 in print_apacket (ptr=<optimized out>, ptr_len=<optimized out>, hdr=<optimized out>)
    at /usr/src/usr.sbin/usbdump/usbdump.c:495
#5  print_packets (data=0x800644000 "\f;2\331\366\067\335\233\225\377\262!\226\237\066d\001\245SSSS", datalen=<optimized out>)
    at /usr/src/usr.sbin/usbdump/usbdump.c:631
#6  0x0000000000203104 in read_file (p=<optimized out>) at /usr/src/usr.sbin/usbdump/usbdump.c:676
#7  0x0000000000202e1d in main (argc=3, argv=0x7fffffffeab8) at /usr/src/usr.sbin/usbdump/usbdump.c:888
(gdb) up 5
#5  print_packets (data=0x800644000 "\f;2\331\366\067\335\233\225\377\262!\226\237\066d\001\245SSSS", datalen=<optimized out>)
    at /usr/src/usr.sbin/usbdump/usbdump.c:631
631    				print_apacket(&temp, ptr +
(gdb)  list 605
600    			if (next <= ptr)
601    				err(EXIT_FAILURE, "Invalid length");
602    		}
603    	}
604
605    	static void
606    	print_packets(uint8_t *data, const int datalen)
607    	{
608    		struct header_32 temp;
609    		uint8_t *ptr;
(gdb)
610    		uint8_t *next;
611
612    		for (ptr = data; ptr < (data + datalen); ptr = next) {
613
614    			const struct header_32 *hdr32;
615
616    			hdr32 = (const struct header_32 *)ptr;
617
618    			temp.ts_sec = le32toh(hdr32->ts_sec);
619    			temp.ts_usec = le32toh(hdr32->ts_usec);
(gdb)
620    			temp.caplen = le32toh(hdr32->caplen);
621    			temp.datalen = le32toh(hdr32->datalen);
622    			temp.hdrlen = hdr32->hdrlen;
623    			temp.align = hdr32->align;
624
625    			next = ptr + roundup2(temp.hdrlen + temp.caplen, temp.align);
626
627    			if (next <= ptr)
628    				err(EXIT_FAILURE, "Invalid length");
629
(gdb)
630    			if (verbose >= 0 || r_arg != NULL || b_arg != NULL) {
631    				print_apacket(&temp, ptr +
632    				    temp.hdrlen, temp.caplen);
633    			}
634    			pkt_captured++;
635    		}
636    	}


To fix the crash input to be realistic, I set the magic value, major value to 0, and minor value (of 3, versus 2) for the struct usbcap_filehdr. I only tested with minor value set to 3 and not 2, but it would seem, regardless, to likely want to adjust how that parsing is done. Attached is the input sample.

I have not worked up a patch, but mostly because I did this in some spare cycles and I do not really know this code so well to produce a solution. :( I know that is not very helpful, but figured I should at least file the bug.