[PATCH 6.1 061/131] net: nfc: fix races in nfc_llcp_sock_get() and nfc_llcp_sock_get_sn()

Greg Kroah-Hartman
2023-10-16T08:57:47Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 31c07dffafce914c1d1543c135382a11ff058d93 ]

Sili Luo reported a race in nfc_llcp_sock_get(), leading to UAF.

Getting a reference on the socket found in a lookup while
holding a lock should happen before releasing the lock.

nfc_llcp_sock_get_sn() has a similar problem.

Finally nfc_llcp_recv_snl() needs to make sure the socket
found by nfc_llcp_sock_from_sn() does not disappear.

Fixes: 8f50020ed9b8 ("NFC: LLCP late binding")
Reported-by: Sili Luo <rootlab@huawei.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willy Tarreau <w@1wt.eu>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231009123110.3735515-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/nfc/llcp_core.c | 30 ++++++++++++------------------
1 file changed, 12 insertions(+), 18 deletions(-)

diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index 6705bb895e239..1dac28136e6a3 100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c
@@ -203,17 +203,13 @@ static struct nfc_llcp_sock *nfc_llcp_sock_get(struct nfc_llcp_local *local,

if (tmp_sock->ssap == ssap && tmp_sock->dsap == dsap) {
llcp_sock = tmp_sock;
+ sock_hold(&llcp_sock->sk);
break;
}
}

read_unlock(&local->sockets.lock);

- if (llcp_sock == NULL)
- return NULL;
-
- sock_hold(&llcp_sock->sk);
-
return llcp_sock;
}

@@ -346,7 +342,8 @@ static int nfc_llcp_wks_sap(const char *service_name, size_t service_name_len)

static
struct nfc_llcp_sock *nfc_llcp_sock_from_sn(struct nfc_llcp_local *local,
- const u8 *sn, size_t sn_len)
+ const u8 *sn, size_t sn_len,
+ bool needref)
{
struct sock *sk;
struct nfc_llcp_sock *llcp_sock, *tmp_sock;
@@ -382,6 +379,8 @@ struct nfc_llcp_sock *nfc_llcp_sock_from_sn(struct nfc_llcp_local *local,

if (memcmp(sn, tmp_sock->service_name, sn_len) == 0) {
llcp_sock = tmp_sock;
+ if (needref)
+ sock_hold(&llcp_sock->sk);
break;
}
}
@@ -423,7 +422,8 @@ u8 nfc_llcp_get_sdp_ssap(struct nfc_llcp_local *local,
* to this service name.
*/
if (nfc_llcp_sock_from_sn(local, sock->service_name,
- sock->service_name_len) != NULL) {
+ sock->service_name_len,
+ false) != NULL) {
mutex_unlock(&local->sdp_lock);

return LLCP_SAP_MAX;
@@ -824,16 +824,7 @@ static struct nfc_llcp_sock *nfc_llcp_connecting_sock_get(struct nfc_llcp_local
static struct nfc_llcp_sock *nfc_llcp_sock_get_sn(struct nfc_llcp_local *local,
const u8 *sn, size_t sn_len)
{
- struct nfc_llcp_sock *llcp_sock;
-
- llcp_sock = nfc_llcp_sock_from_sn(local, sn, sn_len);
-
- if (llcp_sock == NULL)
- return NULL;
-
- sock_hold(&llcp_sock->sk);
-
- return llcp_sock;
+ return nfc_llcp_sock_from_sn(local, sn, sn_len, true);
}

static const u8 *nfc_llcp_connect_sn(const struct sk_buff *skb, size_t *sn_len)
@@ -1298,7 +1289,8 @@ static void nfc_llcp_recv_snl(struct nfc_llcp_local *local,
}

llcp_sock = nfc_llcp_sock_from_sn(local, service_name,
- service_name_len);
+ service_name_len,
+ true);
if (!llcp_sock) {
sap = 0;
goto add_snl;
@@ -1318,6 +1310,7 @@ static void nfc_llcp_recv_snl(struct nfc_llcp_local *local,

if (sap == LLCP_SAP_MAX) {
sap = 0;
+ nfc_llcp_sock_put(llcp_sock);
goto add_snl;
}

@@ -1335,6 +1328,7 @@ static void nfc_llcp_recv_snl(struct nfc_llcp_local *local,

pr_debug("%p %d\n", llcp_sock, sap);

+ nfc_llcp_sock_put(llcp_sock);
add_snl:
sdp = nfc_llcp_build_sdres_tlv(tid, sap);
if (sdp == NULL)
--
2.40.1