Module Name: src
Committed By: bouyer
Date: Tue Mar 22 20:02:36 UTC 2011
Modified Files:
src/sys/net [netbsd-5-0]: bpf_filter.c
Log Message:
Pull up following revision(s) (requested by spz in ticket #1571):
sys/net/bpf_filter.c: revision 1.36, 1.42 -> 1.46 via patch
Avoid stack memory disclosure by keeping track during filter validation time
of initialized memory. Idea taken from linux.
Use __CTASSERT
Use kmem instead of malloc. Requested by rmind.
Fix userland build.
delint.
the correct check for BPF_K is with BPF_SRC for BPF_ALU ops, from
Guy Harris per PR kern/43185
fixes possible division-by-zero crashes by evil filter expressions
like "len / 0 = 1"
pullup candidate
To generate a diff of this commit:
cvs rdiff -u -r1.35 -r1.35.10.1 src/sys/net/bpf_filter.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/net/bpf_filter.c
diff -u src/sys/net/bpf_filter.c:1.35 src/sys/net/bpf_filter.c:1.35.10.1
--- src/sys/net/bpf_filter.c:1.35 Wed Aug 20 13:01:54 2008
+++ src/sys/net/bpf_filter.c Tue Mar 22 20:02:36 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: bpf_filter.c,v 1.35 2008/08/20 13:01:54 joerg Exp $ */
+/* $NetBSD: bpf_filter.c,v 1.35.10.1 2011/03/22 20:02:36 bouyer Exp $ */
/*-
* Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
@@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bpf_filter.c,v 1.35 2008/08/20 13:01:54 joerg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bpf_filter.c,v 1.35.10.1 2011/03/22 20:02:36 bouyer Exp $");
#if 0
#if !(defined(lint) || defined(KERNEL))
@@ -48,6 +48,7 @@
#include <sys/param.h>
#include <sys/time.h>
+#include <sys/kmem.h>
#include <sys/endian.h>
#define EXTRACT_SHORT(p) be16dec(p)
@@ -147,8 +148,7 @@
A = 0;
X = 0;
--pc;
- /* CONSTCOND */
- while (1) {
+ for (;;) {
++pc;
switch (pc->code) {
@@ -157,6 +157,7 @@
return 0;
#else
abort();
+ /*NOTREACHED*/
#endif
case BPF_RET|BPF_K:
return (u_int)pc->k;
@@ -461,16 +462,38 @@
* The kernel needs to be able to verify an application's filter code.
* Otherwise, a bogus program could easily crash the system.
*/
+CTASSERT(BPF_MEMWORDS == sizeof(uint16_t) * NBBY);
+
int
-bpf_validate(struct bpf_insn *f, int len)
+bpf_validate(struct bpf_insn *f, int signed_len)
{
- u_int i, from;
- struct bpf_insn *p;
+ u_int i, from, len, ok = 0;
+ const struct bpf_insn *p;
+#if defined(KERNEL) || defined(_KERNEL)
+ uint16_t *mem, invalid;
+ size_t size;
+#endif
- if (len < 1 || len > BPF_MAXINSNS)
+ len = (u_int)signed_len;
+ if (len < 1)
+ return 0;
+#if defined(KERNEL) || defined(_KERNEL)
+ if (len > BPF_MAXINSNS)
+ return 0;
+#endif
+ if (BPF_CLASS(f[len - 1].code) != BPF_RET)
return 0;
+#if defined(KERNEL) || defined(_KERNEL)
+ mem = kmem_zalloc(size = sizeof(*mem) * len, KM_SLEEP);
+ invalid = ~0; /* All is invalid on startup */
+#endif
+
for (i = 0; i < len; ++i) {
+#if defined(KERNEL) || defined(_KERNEL)
+ /* blend in any invalid bits for current pc */
+ invalid |= mem[i];
+#endif
p = &f[i];
switch (BPF_CLASS(p->code)) {
/*
@@ -480,8 +503,22 @@
case BPF_LDX:
switch (BPF_MODE(p->code)) {
case BPF_MEM:
+ /*
+ * There's no maximum packet data size
+ * in userland. The runtime packet length
+ * check suffices.
+ */
+#if defined(KERNEL) || defined(_KERNEL)
+ /*
+ * More strict check with actual packet length
+ * is done runtime.
+ */
if (p->k >= BPF_MEMWORDS)
- return 0;
+ goto out;
+ /* check for current memory invalid */
+ if (invalid & (1 << p->k))
+ goto out;
+#endif
break;
case BPF_ABS:
case BPF_IND:
@@ -490,13 +527,17 @@
case BPF_LEN:
break;
default:
- return 0;
+ goto out;
}
break;
case BPF_ST:
case BPF_STX:
if (p->k >= BPF_MEMWORDS)
- return 0;
+ goto out;
+#if defined(KERNEL) || defined(_KERNEL)
+ /* validate the memory word */
+ invalid &= ~(1 << p->k);
+#endif
break;
case BPF_ALU:
switch (BPF_OP(p->code)) {
@@ -513,11 +554,11 @@
/*
* Check for constant division by 0.
*/
- if (BPF_RVAL(p->code) == BPF_K && p->k == 0)
- return 0;
+ if (BPF_SRC(p->code) == BPF_K && p->k == 0)
+ goto out;
break;
default:
- return 0;
+ goto out;
}
break;
case BPF_JMP:
@@ -540,18 +581,37 @@
from = i + 1;
switch (BPF_OP(p->code)) {
case BPF_JA:
- if (from + p->k < from || from + p->k >= len)
- return 0;
+ if (from + p->k >= len)
+ goto out;
+#if defined(KERNEL) || defined(_KERNEL)
+ if (from + p->k < from)
+ goto out;
+ /*
+ * mark the currently invalid bits for the
+ * destination
+ */
+ mem[from + p->k] |= invalid;
+ invalid = 0;
+#endif
break;
case BPF_JEQ:
case BPF_JGT:
case BPF_JGE:
case BPF_JSET:
if (from + p->jt >= len || from + p->jf >= len)
- return 0;
+ goto out;
+#if defined(KERNEL) || defined(_KERNEL)
+ /*
+ * mark the currently invalid bits for both
+ * possible jump destinations
+ */
+ mem[from + p->jt] |= invalid;
+ mem[from + p->jf] |= invalid;
+ invalid = 0;
+#endif
break;
default:
- return 0;
+ goto out;
}
break;
case BPF_RET:
@@ -559,10 +619,14 @@
case BPF_MISC:
break;
default:
- return 0;
+ goto out;
}
}
-
- return BPF_CLASS(f[len - 1].code) == BPF_RET;
+ ok = 1;
+out:
+#if defined(KERNEL) || defined(_KERNEL)
+ kmem_free(mem, size);
+#endif
+ return ok;
}
#endif
