[src/trunk]: src/sys/net PR/48198: Peter Bex: Avoid kernel panic caused by se...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/180d4b32fbb0
branches:  trunk
changeset: 789836:180d4b32fbb0
user:      christos <christos%NetBSD.org@localhost>
date:      Mon Sep 09 20:53:51 2013 +0000

description:
PR/48198: Peter Bex: Avoid kernel panic caused by setting a very small bpf
buffer size.
XXX: Pullup -6

diffstat:

 sys/net/bpf.c |  45 +++++++++++++++++++++++++--------------------
 1 files changed, 25 insertions(+), 20 deletions(-)

diffs (94 lines):

diff -r acdbe43ef933 -r 180d4b32fbb0 sys/net/bpf.c
--- a/sys/net/bpf.c     Mon Sep 09 19:47:38 2013 +0000
+++ b/sys/net/bpf.c     Mon Sep 09 20:53:51 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: bpf.c,v 1.175 2013/08/30 15:00:08 rmind Exp $  */
+/*     $NetBSD: bpf.c,v 1.176 2013/09/09 20:53:51 christos Exp $       */
 
 /*
  * Copyright (c) 1990, 1991, 1993
@@ -39,7 +39,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bpf.c,v 1.175 2013/08/30 15:00:08 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bpf.c,v 1.176 2013/09/09 20:53:51 christos Exp $");
 
 #if defined(_KERNEL_OPT)
 #include "opt_bpf.h"
@@ -1576,11 +1576,8 @@
 catchpacket(struct bpf_d *d, u_char *pkt, u_int pktlen, u_int snaplen,
     void *(*cpfn)(void *, const void *, size_t), struct timespec *ts)
 {
-       struct bpf_hdr *hp;
-#ifdef _LP64
-       struct bpf_hdr32 *hp32;
-#endif
-       int totlen, curlen;
+       char *h;
+       int totlen, curlen, caplen;
        int hdrlen = bpf_hdrlen(d);
        int do_wakeup = 0;
 
@@ -1595,6 +1592,13 @@
        totlen = hdrlen + min(snaplen, pktlen);
        if (totlen > d->bd_bufsize)
                totlen = d->bd_bufsize;
+       /*
+        * If we adjusted totlen to fit the bufsize, it could be that
+        * totlen is smaller than hdrlen because of the link layer header.
+        */
+       caplen = totlen - hdrlen;
+       if (caplen < 0)
+               caplen = 0;
 
        /*
         * Round up the end of the previous packet to the next longword.
@@ -1635,33 +1639,34 @@
        /*
         * Append the bpf header.
         */
+       h = (char *)d->bd_sbuf + curlen;
 #ifdef _LP64
        if (d->bd_compat32) {
-               hp32 = (struct bpf_hdr32 *)((char *)d->bd_sbuf + curlen);
+               struct bpf_hdr32 *hp32;
+
+               hp32 = (struct bpf_hdr32 *)h;
                hp32->bh_tstamp.tv_sec = ts->tv_sec;
                hp32->bh_tstamp.tv_usec = ts->tv_nsec / 1000;
                hp32->bh_datalen = pktlen;
                hp32->bh_hdrlen = hdrlen;
-               /*
-                * Copy the packet data into the store buffer and update its length.
-                */
-               (*cpfn)((u_char *)hp32 + hdrlen, pkt,
-                   (hp32->bh_caplen = totlen - hdrlen));
+               hp32->bh_caplen = caplen;
        } else
 #endif
        {
-               hp = (struct bpf_hdr *)((char *)d->bd_sbuf + curlen);
+               struct bpf_hdr *hp;
+
+               hp = (struct bpf_hdr *)h;
                hp->bh_tstamp.tv_sec = ts->tv_sec;
                hp->bh_tstamp.tv_usec = ts->tv_nsec / 1000;
                hp->bh_datalen = pktlen;
                hp->bh_hdrlen = hdrlen;
-               /*
-                * Copy the packet data into the store buffer and update
-                * its length.
-                */
-               (*cpfn)((u_char *)hp + hdrlen, pkt,
-                   (hp->bh_caplen = totlen - hdrlen));
+               hp->bh_caplen = caplen;
        }
+
+       /*
+        * Copy the packet data into the store buffer and update its length.
+        */
+       (*cpfn)(h + hdrlen, pkt, caplen);
        d->bd_slen = curlen + totlen;
 
        /*