Merge branch 'bpf, sockmap: Fix infinite recursion in sock_map_close'

Jakub Sitnicki says:

====================

This patch set addresses the syzbot report in [1].

Patch #1 has been suggested by Eric [2]. I extended it to cover the rest of
sock_map proto callbacks. Otherwise we would still overflow the stack.

Patch #2 contains the actual fix and bug analysis.
Patches #3 & #4 add coverage to selftests to trigger the bug.

[1] https://lore.kernel.org/all/00000000000073b14905ef2e7401@google.com/
[2] https://lore.kernel.org/all/CANn89iK2UN1FmdUcH12fv_xiZkv2G+Nskvmq7fG6aA_6VKRf6g@mail.gmail.com/
---
v1 -> v2:
v1: https://lore.kernel.org/r/20230113-sockmap-fix-v1-0-d3cad092ee10@cloudflare.com
[v1 didn't hit bpf@ ML by mistake]

 * pull in Eric's patch to protect against recursion loop bugs (Eric)
 * add a macro helper to check if pointer is inside a memory range (Eric)
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/util_macros.h

@@ -38,4 +38,16 @@
  */
 #define find_closest_descending(x, a, as) __find_closest(x, a, as, >=)
 
+/**
+ * is_insidevar - check if the @ptr points inside the @var memory range.
+ * @ptr:	the pointer to a memory address.
+ * @var:	the variable which address and size identify the memory range.
+ *
+ * Evaluates to true if the address in @ptr lies within the memory
+ * range allocated to @var.
+ */
+#define is_insidevar(ptr, var)						\
+	((uintptr_t)(ptr) >= (uintptr_t)(var) &&			\
+	 (uintptr_t)(ptr) <  (uintptr_t)(var) + sizeof(var))
+
 #endif

net/core/sock_map.c

@@ -1569,15 +1569,16 @@ void sock_map_unhash(struct sock *sk)
 	psock = sk_psock(sk);
 	if (unlikely(!psock)) {
 		rcu_read_unlock();
-		if (sk->sk_prot->unhash)
-			sk->sk_prot->unhash(sk);
-		return;
+		saved_unhash = READ_ONCE(sk->sk_prot)->unhash;
+	} else {
+		saved_unhash = psock->saved_unhash;
+		sock_map_remove_links(sk, psock);
+		rcu_read_unlock();
 	}
-
-	saved_unhash = psock->saved_unhash;
-	sock_map_remove_links(sk, psock);
-	rcu_read_unlock();
-	saved_unhash(sk);
+	if (WARN_ON_ONCE(saved_unhash == sock_map_unhash))
+		return;
+	if (saved_unhash)
+		saved_unhash(sk);
 }
 EXPORT_SYMBOL_GPL(sock_map_unhash);
 
@@ -1590,17 +1591,18 @@ void sock_map_destroy(struct sock *sk)
 	psock = sk_psock_get(sk);
 	if (unlikely(!psock)) {
 		rcu_read_unlock();
-		if (sk->sk_prot->destroy)
-			sk->sk_prot->destroy(sk);
-		return;
+		saved_destroy = READ_ONCE(sk->sk_prot)->destroy;
+	} else {
+		saved_destroy = psock->saved_destroy;
+		sock_map_remove_links(sk, psock);
+		rcu_read_unlock();
+		sk_psock_stop(psock);
+		sk_psock_put(sk, psock);
 	}
-
-	saved_destroy = psock->saved_destroy;
-	sock_map_remove_links(sk, psock);
-	rcu_read_unlock();
-	sk_psock_stop(psock);
-	sk_psock_put(sk, psock);
-	saved_destroy(sk);
+	if (WARN_ON_ONCE(saved_destroy == sock_map_destroy))
+		return;
+	if (saved_destroy)
+		saved_destroy(sk);
 }
 EXPORT_SYMBOL_GPL(sock_map_destroy);
 
@@ -1615,16 +1617,21 @@ void sock_map_close(struct sock *sk, long timeout)
 	if (unlikely(!psock)) {
 		rcu_read_unlock();
 		release_sock(sk);
-		return sk->sk_prot->close(sk, timeout);
+		saved_close = READ_ONCE(sk->sk_prot)->close;
+	} else {
+		saved_close = psock->saved_close;
+		sock_map_remove_links(sk, psock);
+		rcu_read_unlock();
+		sk_psock_stop(psock);
+		release_sock(sk);
+		cancel_work_sync(&psock->work);
+		sk_psock_put(sk, psock);
 	}
-
-	saved_close = psock->saved_close;
-	sock_map_remove_links(sk, psock);
-	rcu_read_unlock();
-	sk_psock_stop(psock);
-	release_sock(sk);
-	cancel_work_sync(&psock->work);
-	sk_psock_put(sk, psock);
+	/* Make sure we do not recurse. This is a bug.
+	 * Leak the socket instead of crashing on a stack overflow.
+	 */
+	if (WARN_ON_ONCE(saved_close == sock_map_close))
+		return;
 	saved_close(sk, timeout);
 }
 EXPORT_SYMBOL_GPL(sock_map_close);

net/ipv4/tcp_bpf.c

@@ -6,6 +6,7 @@
 #include <linux/bpf.h>
 #include <linux/init.h>
 #include <linux/wait.h>
+#include <linux/util_macros.h>
 
 #include <net/inet_common.h>
 #include <net/tls.h>
@@ -639,10 +640,9 @@ EXPORT_SYMBOL_GPL(tcp_bpf_update_proto);
  */
 void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
 {
-	int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
 	struct proto *prot = newsk->sk_prot;
 
-	if (prot == &tcp_bpf_prots[family][TCP_BPF_BASE])
+	if (is_insidevar(prot, tcp_bpf_prots))
 		newsk->sk_prot = sk->sk_prot_creator;
 }
 #endif /* CONFIG_BPF_SYSCALL */

tools/testing/selftests/bpf/prog_tests/sockmap_listen.c

@@ -30,6 +30,8 @@
 #define MAX_STRERR_LEN 256
 #define MAX_TEST_NAME 80
 
+#define __always_unused	__attribute__((__unused__))
+
 #define _FAIL(errnum, fmt...)                                                  \
 	({                                                                     \
 		error_at_line(0, (errnum), __func__, __LINE__, fmt);           \
@@ -321,7 +323,8 @@ static int socket_loopback(int family, int sotype)
 	return socket_loopback_reuseport(family, sotype, -1);
 }
 
-static void test_insert_invalid(int family, int sotype, int mapfd)
+static void test_insert_invalid(struct test_sockmap_listen *skel __always_unused,
+				int family, int sotype, int mapfd)
 {
 	u32 key = 0;
 	u64 value;
@@ -338,7 +341,8 @@ static void test_insert_invalid(int family, int sotype, int mapfd)
 		FAIL_ERRNO("map_update: expected EBADF");
 }
 
-static void test_insert_opened(int family, int sotype, int mapfd)
+static void test_insert_opened(struct test_sockmap_listen *skel __always_unused,
+			       int family, int sotype, int mapfd)
 {
 	u32 key = 0;
 	u64 value;
@@ -359,7 +363,8 @@ static void test_insert_opened(int family, int sotype, int mapfd)
 	xclose(s);
 }
 
-static void test_insert_bound(int family, int sotype, int mapfd)
+static void test_insert_bound(struct test_sockmap_listen *skel __always_unused,
+			      int family, int sotype, int mapfd)
 {
 	struct sockaddr_storage addr;
 	socklen_t len;
@@ -386,7 +391,8 @@ static void test_insert_bound(int family, int sotype, int mapfd)
 	xclose(s);
 }
 
-static void test_insert(int family, int sotype, int mapfd)
+static void test_insert(struct test_sockmap_listen *skel __always_unused,
+			int family, int sotype, int mapfd)
 {
 	u64 value;
 	u32 key;
@@ -402,7 +408,8 @@ static void test_insert(int family, int sotype, int mapfd)
 	xclose(s);
 }
 
-static void test_delete_after_insert(int family, int sotype, int mapfd)
+static void test_delete_after_insert(struct test_sockmap_listen *skel __always_unused,
+				     int family, int sotype, int mapfd)
 {
 	u64 value;
 	u32 key;
@@ -419,7 +426,8 @@ static void test_delete_after_insert(int family, int sotype, int mapfd)
 	xclose(s);
 }
 
-static void test_delete_after_close(int family, int sotype, int mapfd)
+static void test_delete_after_close(struct test_sockmap_listen *skel __always_unused,
+				    int family, int sotype, int mapfd)
 {
 	int err, s;
 	u64 value;
@@ -442,7 +450,8 @@ static void test_delete_after_close(int family, int sotype, int mapfd)
 		FAIL_ERRNO("map_delete: expected EINVAL/EINVAL");
 }
 
-static void test_lookup_after_insert(int family, int sotype, int mapfd)
+static void test_lookup_after_insert(struct test_sockmap_listen *skel __always_unused,
+				     int family, int sotype, int mapfd)
 {
 	u64 cookie, value;
 	socklen_t len;
@@ -470,7 +479,8 @@ static void test_lookup_after_insert(int family, int sotype, int mapfd)
 	xclose(s);
 }
 
-static void test_lookup_after_delete(int family, int sotype, int mapfd)
+static void test_lookup_after_delete(struct test_sockmap_listen *skel __always_unused,
+				     int family, int sotype, int mapfd)
 {
 	int err, s;
 	u64 value;
@@ -493,7 +503,8 @@ static void test_lookup_after_delete(int family, int sotype, int mapfd)
 	xclose(s);
 }
 
-static void test_lookup_32_bit_value(int family, int sotype, int mapfd)
+static void test_lookup_32_bit_value(struct test_sockmap_listen *skel __always_unused,
+				     int family, int sotype, int mapfd)
 {
 	u32 key, value32;
 	int err, s;
@@ -523,7 +534,8 @@ static void test_lookup_32_bit_value(int family, int sotype, int mapfd)
 	xclose(s);
 }
 
-static void test_update_existing(int family, int sotype, int mapfd)
+static void test_update_existing(struct test_sockmap_listen *skel __always_unused,
+				 int family, int sotype, int mapfd)
 {
 	int s1, s2;
 	u64 value;
@@ -551,7 +563,7 @@ static void test_update_existing(int family, int sotype, int mapfd)
 /* Exercise the code path where we destroy child sockets that never
  * got accept()'ed, aka orphans, when parent socket gets closed.
  */
-static void test_destroy_orphan_child(int family, int sotype, int mapfd)
+static void do_destroy_orphan_child(int family, int sotype, int mapfd)
 {
 	struct sockaddr_storage addr;
 	socklen_t len;
@@ -582,10 +594,38 @@ static void test_destroy_orphan_child(int family, int sotype, int mapfd)
 	xclose(s);
 }
 
+static void test_destroy_orphan_child(struct test_sockmap_listen *skel,
+				      int family, int sotype, int mapfd)
+{
+	int msg_verdict = bpf_program__fd(skel->progs.prog_msg_verdict);
+	int skb_verdict = bpf_program__fd(skel->progs.prog_skb_verdict);
+	const struct test {
+		int progfd;
+		enum bpf_attach_type atype;
+	} tests[] = {
+		{ -1, -1 },
+		{ msg_verdict, BPF_SK_MSG_VERDICT },
+		{ skb_verdict, BPF_SK_SKB_VERDICT },
+	};
+	const struct test *t;
+
+	for (t = tests; t < tests + ARRAY_SIZE(tests); t++) {
+		if (t->progfd != -1 &&
+		    xbpf_prog_attach(t->progfd, mapfd, t->atype, 0) != 0)
+			return;
+
+		do_destroy_orphan_child(family, sotype, mapfd);
+
+		if (t->progfd != -1)
+			xbpf_prog_detach2(t->progfd, mapfd, t->atype);
+	}
+}
+
 /* Perform a passive open after removing listening socket from SOCKMAP
  * to ensure that callbacks get restored properly.
  */
-static void test_clone_after_delete(int family, int sotype, int mapfd)
+static void test_clone_after_delete(struct test_sockmap_listen *skel __always_unused,
+				    int family, int sotype, int mapfd)
 {
 	struct sockaddr_storage addr;
 	socklen_t len;
@@ -621,7 +661,8 @@ static void test_clone_after_delete(int family, int sotype, int mapfd)
  * SOCKMAP, but got accept()'ed only after the parent has been removed
  * from SOCKMAP, gets cloned without parent psock state or callbacks.
  */
-static void test_accept_after_delete(int family, int sotype, int mapfd)
+static void test_accept_after_delete(struct test_sockmap_listen *skel __always_unused,
+				     int family, int sotype, int mapfd)
 {
 	struct sockaddr_storage addr;
 	const u32 zero = 0;
@@ -675,7 +716,8 @@ static void test_accept_after_delete(int family, int sotype, int mapfd)
 /* Check that child socket that got created and accepted while parent
  * was in a SOCKMAP is cloned without parent psock state or callbacks.
  */
-static void test_accept_before_delete(int family, int sotype, int mapfd)
+static void test_accept_before_delete(struct test_sockmap_listen *skel __always_unused,
+				      int family, int sotype, int mapfd)
 {
 	struct sockaddr_storage addr;
 	const u32 zero = 0, one = 1;
@@ -784,7 +826,8 @@ static void *connect_accept_thread(void *arg)
 	return NULL;
 }
 
-static void test_syn_recv_insert_delete(int family, int sotype, int mapfd)
+static void test_syn_recv_insert_delete(struct test_sockmap_listen *skel __always_unused,
+					int family, int sotype, int mapfd)
 {
 	struct connect_accept_ctx ctx = { 0 };
 	struct sockaddr_storage addr;
@@ -847,7 +890,8 @@ static void *listen_thread(void *arg)
 	return NULL;
 }
 
-static void test_race_insert_listen(int family, int socktype, int mapfd)
+static void test_race_insert_listen(struct test_sockmap_listen *skel __always_unused,
+				    int family, int socktype, int mapfd)
 {
 	struct connect_accept_ctx ctx = { 0 };
 	const u32 zero = 0;
@@ -1473,7 +1517,8 @@ static void test_ops(struct test_sockmap_listen *skel, struct bpf_map *map,
 		     int family, int sotype)
 {
 	const struct op_test {
-		void (*fn)(int family, int sotype, int mapfd);
+		void (*fn)(struct test_sockmap_listen *skel,
+			   int family, int sotype, int mapfd);
 		const char *name;
 		int sotype;
 	} tests[] = {
@@ -1520,7 +1565,7 @@ static void test_ops(struct test_sockmap_listen *skel, struct bpf_map *map,
 		if (!test__start_subtest(s))
 			continue;
 
-		t->fn(family, sotype, map_fd);
+		t->fn(skel, family, sotype, map_fd);
 		test_ops_cleanup(map);
 	}
 }