This is a note to let you know that I've just added the patch titled
net: skb_find_text: Ignore patterns extending past 'to'
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-skb_find_text-ignore-patterns-extending-past-to.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 526d2a04e55176861a1669aa9cd567b650dd8185
Author: Phil Sutter <phil@xxxxxx>
Date: Tue Oct 17 11:39:06 2023 +0200
net: skb_find_text: Ignore patterns extending past 'to'
[ Upstream commit c4eee56e14fe001e1cff54f0b438a5e2d0dd7454 ]
Assume that caller's 'to' offset really represents an upper boundary for
the pattern search, so patterns extending past this offset are to be
rejected.
The old behaviour also was kind of inconsistent when it comes to
fragmentation (or otherwise non-linear skbs): If the pattern started in
between 'to' and 'from' offsets but extended to the next fragment, it
was not found if 'to' offset was still within the current fragment.
Test the new behaviour in a kselftest using iptables' string match.
Suggested-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Fixes: f72b948dcbb8 ("[NET]: skb_find_text ignores to argument")
Signed-off-by: Phil Sutter <phil@xxxxxx>
Reviewed-by: Florian Westphal <fw@xxxxxxxxx>
Reviewed-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 8dca4a7ca4a1f..73b1e0e53534e 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3958,6 +3958,7 @@ static void skb_ts_finish(struct ts_config *conf, struct ts_state *state)
unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
unsigned int to, struct ts_config *config)
{
+ unsigned int patlen = config->ops->get_pattern_len(config);
struct ts_state state;
unsigned int ret;
@@ -3969,7 +3970,7 @@ unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
skb_prepare_seq_read(skb, from, to, TS_SKB_CB(&state));
ret = textsearch_find(config, &state);
- return (ret <= to - from ? ret : UINT_MAX);
+ return (ret + patlen <= to - from ? ret : UINT_MAX);
}
EXPORT_SYMBOL(skb_find_text);
diff --git a/tools/testing/selftests/netfilter/Makefile b/tools/testing/selftests/netfilter/Makefile
index ef90aca4cc96a..bced422b78f72 100644
--- a/tools/testing/selftests/netfilter/Makefile
+++ b/tools/testing/selftests/netfilter/Makefile
@@ -7,7 +7,7 @@ TEST_PROGS := nft_trans_stress.sh nft_fib.sh nft_nat.sh bridge_brouter.sh \
nft_queue.sh nft_meta.sh nf_nat_edemux.sh \
ipip-conntrack-mtu.sh conntrack_tcp_unreplied.sh \
conntrack_vrf.sh nft_synproxy.sh rpath.sh nft_audit.sh \
- conntrack_sctp_collision.sh
+ conntrack_sctp_collision.sh xt_string.sh
HOSTPKG_CONFIG := pkg-config
diff --git a/tools/testing/selftests/netfilter/xt_string.sh b/tools/testing/selftests/netfilter/xt_string.sh
new file mode 100755
index 0000000000000..1802653a47287
--- /dev/null
+++ b/tools/testing/selftests/netfilter/xt_string.sh
@@ -0,0 +1,128 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# return code to signal skipped test
+ksft_skip=4
+rc=0
+
+if ! iptables --version >/dev/null 2>&1; then
+ echo "SKIP: Test needs iptables"
+ exit $ksft_skip
+fi
+if ! ip -V >/dev/null 2>&1; then
+ echo "SKIP: Test needs iproute2"
+ exit $ksft_skip
+fi
+if ! nc -h >/dev/null 2>&1; then
+ echo "SKIP: Test needs netcat"
+ exit $ksft_skip
+fi
+
+pattern="foo bar baz"
+patlen=11
+hdrlen=$((20 + 8)) # IPv4 + UDP
+ns="ns-$(mktemp -u XXXXXXXX)"
+trap 'ip netns del $ns' EXIT
+ip netns add "$ns"
+ip -net "$ns" link add d0 type dummy
+ip -net "$ns" link set d0 up
+ip -net "$ns" addr add 10.1.2.1/24 dev d0
+
+#ip netns exec "$ns" tcpdump -npXi d0 &
+#tcpdump_pid=$!
+#trap 'kill $tcpdump_pid; ip netns del $ns' EXIT
+
+add_rule() { # (alg, from, to)
+ ip netns exec "$ns" \
+ iptables -A OUTPUT -o d0 -m string \
+ --string "$pattern" --algo $1 --from $2 --to $3
+}
+showrules() { # ()
+ ip netns exec "$ns" iptables -v -S OUTPUT | grep '^-A'
+}
+zerorules() {
+ ip netns exec "$ns" iptables -Z OUTPUT
+}
+countrule() { # (pattern)
+ showrules | grep -c -- "$*"
+}
+send() { # (offset)
+ ( for ((i = 0; i < $1 - $hdrlen; i++)); do
+ printf " "
+ done
+ printf "$pattern"
+ ) | ip netns exec "$ns" nc -w 1 -u 10.1.2.2 27374
+}
+
+add_rule bm 1000 1500
+add_rule bm 1400 1600
+add_rule kmp 1000 1500
+add_rule kmp 1400 1600
+
+zerorules
+send 0
+send $((1000 - $patlen))
+if [ $(countrule -c 0 0) -ne 4 ]; then
+ echo "FAIL: rules match data before --from"
+ showrules
+ ((rc--))
+fi
+
+zerorules
+send 1000
+send $((1400 - $patlen))
+if [ $(countrule -c 2) -ne 2 ]; then
+ echo "FAIL: only two rules should match at low offset"
+ showrules
+ ((rc--))
+fi
+
+zerorules
+send $((1500 - $patlen))
+if [ $(countrule -c 1) -ne 4 ]; then
+ echo "FAIL: all rules should match at end of packet"
+ showrules
+ ((rc--))
+fi
+
+zerorules
+send 1495
+if [ $(countrule -c 1) -ne 1 ]; then
+ echo "FAIL: only kmp with proper --to should match pattern spanning fragments"
+ showrules
+ ((rc--))
+fi
+
+zerorules
+send 1500
+if [ $(countrule -c 1) -ne 2 ]; then
+ echo "FAIL: two rules should match pattern at start of second fragment"
+ showrules
+ ((rc--))
+fi
+
+zerorules
+send $((1600 - $patlen))
+if [ $(countrule -c 1) -ne 2 ]; then
+ echo "FAIL: two rules should match pattern at end of largest --to"
+ showrules
+ ((rc--))
+fi
+
+zerorules
+send $((1600 - $patlen + 1))
+if [ $(countrule -c 1) -ne 0 ]; then
+ echo "FAIL: no rules should match pattern extending largest --to"
+ showrules
+ ((rc--))
+fi
+
+zerorules
+send 1600
+if [ $(countrule -c 1) -ne 0 ]; then
+ echo "FAIL: no rule should match pattern past largest --to"
+ showrules
+ ((rc--))
+fi
+
+exit $rc
