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Message-ID: <aa9e49a1-7450-4df4-8848-8b2b5a868c28@siddh.me>
Date: Sat, 9 Dec 2023 16:09:33 +0530
From: Siddh Raman Pant <code@...dh.me>
To: syzbot+bbe84a4010eeea00982d@...kaller.appspotmail.com
Cc: code@...dh.me, linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] [nfc?] KASAN: slab-use-after-free Read in
nfc_alloc_send_skb
Final test
#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
---
net/nfc/llcp_core.c | 55 ++++++++++++++++++++++++++++++++++-----------
1 file changed, 42 insertions(+), 13 deletions(-)
diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index 1dac28136e6a..0ae89ab42aaa 100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c
@@ -145,6 +145,13 @@ static void nfc_llcp_socket_release(struct nfc_llcp_local *local, bool device,
static struct nfc_llcp_local *nfc_llcp_local_get(struct nfc_llcp_local *local)
{
+ /* Since using nfc_llcp_local may result in usage of nfc_dev, whenever
+ * we hold a reference to local, we also need to hold a reference to
+ * the device to avoid UAF.
+ */
+ if (!nfc_get_device(local->dev->idx))
+ return NULL;
+
kref_get(&local->ref);
return local;
@@ -177,10 +184,18 @@ static void local_release(struct kref *ref)
int nfc_llcp_local_put(struct nfc_llcp_local *local)
{
+ struct nfc_dev *dev;
+ int ret;
+
if (local == NULL)
return 0;
- return kref_put(&local->ref, local_release);
+ dev = local->dev;
+
+ ret = kref_put(&local->ref, local_release);
+ nfc_put_device(dev);
+
+ return ret;
}
static struct nfc_llcp_sock *nfc_llcp_sock_get(struct nfc_llcp_local *local,
@@ -930,9 +945,7 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local,
if (sk_acceptq_is_full(parent)) {
reason = LLCP_DM_REJ;
- release_sock(&sock->sk);
- sock_put(&sock->sk);
- goto fail;
+ goto fail_put_sock;
}
if (sock->ssap == LLCP_SDP_UNBOUND) {
@@ -942,9 +955,7 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local,
if (ssap == LLCP_SAP_MAX) {
reason = LLCP_DM_REJ;
- release_sock(&sock->sk);
- sock_put(&sock->sk);
- goto fail;
+ goto fail_put_sock;
}
sock->ssap = ssap;
@@ -953,14 +964,18 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local,
new_sk = nfc_llcp_sock_alloc(NULL, parent->sk_type, GFP_ATOMIC, 0);
if (new_sk == NULL) {
reason = LLCP_DM_REJ;
- release_sock(&sock->sk);
- sock_put(&sock->sk);
- goto fail;
+ goto fail_put_sock;
}
new_sock = nfc_llcp_sock(new_sk);
- new_sock->dev = local->dev;
+
new_sock->local = nfc_llcp_local_get(local);
+ if (!new_sock->local) {
+ reason = LLCP_DM_REJ;
+ goto fail_free_new_sock;
+ }
+
+ new_sock->dev = local->dev;
new_sock->rw = sock->rw;
new_sock->miux = sock->miux;
new_sock->nfc_protocol = sock->nfc_protocol;
@@ -1004,8 +1019,13 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local,
return;
+fail_free_new_sock:
+ sock_put(&new_sock->sk);
+ nfc_llcp_sock_free(new_sock);
+fail_put_sock:
+ release_sock(&sock->sk);
+ sock_put(&sock->sk);
fail:
- /* Send DM */
nfc_llcp_send_dm(local, dsap, ssap, reason);
}
@@ -1597,7 +1617,16 @@ int nfc_llcp_register_device(struct nfc_dev *ndev)
if (local == NULL)
return -ENOMEM;
- local->dev = ndev;
+ /* As we are going to initialize local's refcount, we need to get the
+ * nfc_dev to avoid UAF, otherwise there is no point in continuing.
+ * See nfc_llcp_local_get().
+ */
+ local->dev = nfc_get_device(ndev->idx);
+ if (!local->dev) {
+ kfree(local);
+ return -ENODEV;
+ }
+
INIT_LIST_HEAD(&local->list);
kref_init(&local->ref);
mutex_init(&local->sdp_lock);
--
2.42.0
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