6.12-stable review patch. If anyone has any objections, please let me know.
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From: Matt Johnston matt@codeconstruct.com.au
[ Upstream commit f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc ]
Ensure that the frag_list used for reassembly isn't shared with other packets. This avoids incorrect reassembly when packets are cloned, and prevents a memory leak due to circular references between fragments and their skb_shared_info.
The upcoming MCTP-over-USB driver uses skb_clone which can trigger the problem - other MCTP drivers don't share SKBs.
A kunit test is added to reproduce the issue.
Signed-off-by: Matt Johnston matt@codeconstruct.com.au Fixes: 4a992bbd3650 ("mctp: Implement message fragmentation & reassembly") Reviewed-by: Simon Horman horms@kernel.org Link: https://patch.msgid.link/20250306-matt-mctp-usb-v1-1-085502b3dd28@codeconstr... Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/mctp/route.c | 10 +++- net/mctp/test/route-test.c | 109 +++++++++++++++++++++++++++++++++++++ 2 files changed, 117 insertions(+), 2 deletions(-)
diff --git a/net/mctp/route.c b/net/mctp/route.c index 3f2bd65ff5e3c..4c460160914f0 100644 --- a/net/mctp/route.c +++ b/net/mctp/route.c @@ -332,8 +332,14 @@ static int mctp_frag_queue(struct mctp_sk_key *key, struct sk_buff *skb) & MCTP_HDR_SEQ_MASK;
if (!key->reasm_head) { - key->reasm_head = skb; - key->reasm_tailp = &(skb_shinfo(skb)->frag_list); + /* Since we're manipulating the shared frag_list, ensure it isn't + * shared with any other SKBs. + */ + key->reasm_head = skb_unshare(skb, GFP_ATOMIC); + if (!key->reasm_head) + return -ENOMEM; + + key->reasm_tailp = &(skb_shinfo(key->reasm_head)->frag_list); key->last_seq = this_seq; return 0; } diff --git a/net/mctp/test/route-test.c b/net/mctp/test/route-test.c index 17165b86ce22d..06c1897b685a8 100644 --- a/net/mctp/test/route-test.c +++ b/net/mctp/test/route-test.c @@ -921,6 +921,114 @@ static void mctp_test_route_input_sk_fail_frag(struct kunit *test) __mctp_route_test_fini(test, dev, rt, sock); }
+/* Input route to socket, using a fragmented message created from clones. + */ +static void mctp_test_route_input_cloned_frag(struct kunit *test) +{ + /* 5 packet fragments, forming 2 complete messages */ + const struct mctp_hdr hdrs[5] = { + RX_FRAG(FL_S, 0), + RX_FRAG(0, 1), + RX_FRAG(FL_E, 2), + RX_FRAG(FL_S, 0), + RX_FRAG(FL_E, 1), + }; + struct mctp_test_route *rt; + struct mctp_test_dev *dev; + struct sk_buff *skb[5]; + struct sk_buff *rx_skb; + struct socket *sock; + size_t data_len; + u8 compare[100]; + u8 flat[100]; + size_t total; + void *p; + int rc; + + /* Arbitrary length */ + data_len = 3; + total = data_len + sizeof(struct mctp_hdr); + + __mctp_route_test_init(test, &dev, &rt, &sock, MCTP_NET_ANY); + + /* Create a single skb initially with concatenated packets */ + skb[0] = mctp_test_create_skb(&hdrs[0], 5 * total); + mctp_test_skb_set_dev(skb[0], dev); + memset(skb[0]->data, 0 * 0x11, skb[0]->len); + memcpy(skb[0]->data, &hdrs[0], sizeof(struct mctp_hdr)); + + /* Extract and populate packets */ + for (int i = 1; i < 5; i++) { + skb[i] = skb_clone(skb[i - 1], GFP_ATOMIC); + KUNIT_ASSERT_TRUE(test, skb[i]); + p = skb_pull(skb[i], total); + KUNIT_ASSERT_TRUE(test, p); + skb_reset_network_header(skb[i]); + memcpy(skb[i]->data, &hdrs[i], sizeof(struct mctp_hdr)); + memset(&skb[i]->data[sizeof(struct mctp_hdr)], i * 0x11, data_len); + } + for (int i = 0; i < 5; i++) + skb_trim(skb[i], total); + + /* SOM packets have a type byte to match the socket */ + skb[0]->data[4] = 0; + skb[3]->data[4] = 0; + + skb_dump("pkt1 ", skb[0], false); + skb_dump("pkt2 ", skb[1], false); + skb_dump("pkt3 ", skb[2], false); + skb_dump("pkt4 ", skb[3], false); + skb_dump("pkt5 ", skb[4], false); + + for (int i = 0; i < 5; i++) { + KUNIT_EXPECT_EQ(test, refcount_read(&skb[i]->users), 1); + /* Take a reference so we can check refcounts at the end */ + skb_get(skb[i]); + } + + /* Feed the fragments into MCTP core */ + for (int i = 0; i < 5; i++) { + rc = mctp_route_input(&rt->rt, skb[i]); + KUNIT_EXPECT_EQ(test, rc, 0); + } + + /* Receive first reassembled message */ + rx_skb = skb_recv_datagram(sock->sk, MSG_DONTWAIT, &rc); + KUNIT_EXPECT_EQ(test, rc, 0); + KUNIT_EXPECT_EQ(test, rx_skb->len, 3 * data_len); + rc = skb_copy_bits(rx_skb, 0, flat, rx_skb->len); + for (int i = 0; i < rx_skb->len; i++) + compare[i] = (i / data_len) * 0x11; + /* Set type byte */ + compare[0] = 0; + + KUNIT_EXPECT_MEMEQ(test, flat, compare, rx_skb->len); + KUNIT_EXPECT_EQ(test, refcount_read(&rx_skb->users), 1); + kfree_skb(rx_skb); + + /* Receive second reassembled message */ + rx_skb = skb_recv_datagram(sock->sk, MSG_DONTWAIT, &rc); + KUNIT_EXPECT_EQ(test, rc, 0); + KUNIT_EXPECT_EQ(test, rx_skb->len, 2 * data_len); + rc = skb_copy_bits(rx_skb, 0, flat, rx_skb->len); + for (int i = 0; i < rx_skb->len; i++) + compare[i] = (i / data_len + 3) * 0x11; + /* Set type byte */ + compare[0] = 0; + + KUNIT_EXPECT_MEMEQ(test, flat, compare, rx_skb->len); + KUNIT_EXPECT_EQ(test, refcount_read(&rx_skb->users), 1); + kfree_skb(rx_skb); + + /* Check input skb refcounts */ + for (int i = 0; i < 5; i++) { + KUNIT_EXPECT_EQ(test, refcount_read(&skb[i]->users), 1); + kfree_skb(skb[i]); + } + + __mctp_route_test_fini(test, dev, rt, sock); +} + #if IS_ENABLED(CONFIG_MCTP_FLOWS)
static void mctp_test_flow_init(struct kunit *test, @@ -1144,6 +1252,7 @@ static struct kunit_case mctp_test_cases[] = { KUNIT_CASE(mctp_test_packet_flow), KUNIT_CASE(mctp_test_fragment_flow), KUNIT_CASE(mctp_test_route_output_key_create), + KUNIT_CASE(mctp_test_route_input_cloned_frag), {} };