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Thu, 19 Feb 2026 07:57:57 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id UYgaFoXClml2SwAAD6G6ig (envelope-from ); Thu, 19 Feb 2026 07:57:57 +0000 From: Fernando Fernandez Mancera To: netdev@vger.kernel.org Cc: rds-devel@oss.oracle.com, linux-rdma@vger.kernel.org, gerd.rausch@oracle.com, horms@kernel.org, pabeni@redhat.com, kuba@kernel.org, edumazet@google.com, davem@davemloft.net, allison.henderson@oracle.com, Fernando Fernandez Mancera , syzbot+5efae91f60932839f0a5@syzkaller.appspotmail.com Subject: [PATCH net v3] net/rds: fix recursive lock in rds_tcp_conn_slots_available Date: Thu, 19 Feb 2026 08:57:38 +0100 Message-ID: <20260219075738.4403-1-fmancera@suse.de> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-1.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo]; RCPT_COUNT_TWELVE(0.00)[12]; MIME_TRACE(0.00)[0:+]; FUZZY_RATELIMITED(0.00)[rspamd.com]; TAGGED_RCPT(0.00)[5efae91f60932839f0a5]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_DN_SOME(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCVD_TLS_ALL(0.00)[] X-Spam-Flag: NO X-Spam-Score: -1.30 X-Spam-Level: syzbot reported a recursive lock warning in rds_tcp_get_peer_sport() as it calls inet6_getname() which acquires the socket lock that was already held by __release_sock(). kworker/u8:6/2985 is trying to acquire lock: ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline] ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: inet6_getname+0x15d/0x650 net/ipv6/af_inet6.c:533 but task is already holding lock: ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline] ffff88807a07aa20 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: tcp_sock_set_cork+0x2c/0x2e0 net/ipv4/tcp.c:3694 lock_sock_nested+0x48/0x100 net/core/sock.c:3780 lock_sock include/net/sock.h:1709 [inline] inet6_getname+0x15d/0x650 net/ipv6/af_inet6.c:533 rds_tcp_get_peer_sport net/rds/tcp_listen.c:70 [inline] rds_tcp_conn_slots_available+0x288/0x470 net/rds/tcp_listen.c:149 rds_recv_hs_exthdrs+0x60f/0x7c0 net/rds/recv.c:265 rds_recv_incoming+0x9f6/0x12d0 net/rds/recv.c:389 rds_tcp_data_recv+0x7f1/0xa40 net/rds/tcp_recv.c:243 __tcp_read_sock+0x196/0x970 net/ipv4/tcp.c:1702 rds_tcp_read_sock net/rds/tcp_recv.c:277 [inline] rds_tcp_data_ready+0x369/0x950 net/rds/tcp_recv.c:331 tcp_rcv_established+0x19e9/0x2670 net/ipv4/tcp_input.c:6675 tcp_v6_do_rcv+0x8eb/0x1ba0 net/ipv6/tcp_ipv6.c:1609 sk_backlog_rcv include/net/sock.h:1185 [inline] __release_sock+0x1b8/0x3a0 net/core/sock.c:3213 Reading from the socket struct directly is safe from possible paths. For rds_tcp_accept_one(), the socket has just been accepted and is not yet exposed to concurrent access. For rds_tcp_conn_slots_available(), direct access avoids the recursive deadlock seen during backlog processing where the socket lock is already held from the __release_sock(). However, rds_tcp_conn_slots_available() is also called from the normal softirq path via tcp_data_ready() where the lock is not held. This is also safe because inet_dport is a stable 16 bits field. A READ_ONCE() annotation as the value might be accessed lockless in a concurrent access context. Note that it is also safe to call rds_tcp_conn_slots_available() from rds_conn_shutdown() because the fan-out is disabled. Fixes: 9d27a0fb122f ("net/rds: Trigger rds_send_ping() more than once") Reported-by: syzbot+5efae91f60932839f0a5@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=5efae91f60932839f0a5 Signed-off-by: Fernando Fernandez Mancera --- v2: clarified commit message and add a comment around rds_conn_shutdown() path v3: used READ_ONCE() for lockless read and adjusted commit message --- net/rds/connection.c | 3 +++ net/rds/tcp_listen.c | 28 +++++----------------------- 2 files changed, 8 insertions(+), 23 deletions(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index 185f73b01694..a542f94c0214 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -455,6 +455,9 @@ void rds_conn_shutdown(struct rds_conn_path *cp) rcu_read_unlock(); } + /* we do not hold the socket lock here but it is safe because + * fan-out is disabled when calling conn_slots_available() + */ if (conn->c_trans->conn_slots_available) conn->c_trans->conn_slots_available(conn, false); } diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c index 6fb5c928b8fd..dce7ac9d3197 100644 --- a/net/rds/tcp_listen.c +++ b/net/rds/tcp_listen.c @@ -59,30 +59,12 @@ void rds_tcp_keepalive(struct socket *sock) static int rds_tcp_get_peer_sport(struct socket *sock) { - union { - struct sockaddr_storage storage; - struct sockaddr addr; - struct sockaddr_in sin; - struct sockaddr_in6 sin6; - } saddr; - int sport; - - if (kernel_getpeername(sock, &saddr.addr) >= 0) { - switch (saddr.addr.sa_family) { - case AF_INET: - sport = ntohs(saddr.sin.sin_port); - break; - case AF_INET6: - sport = ntohs(saddr.sin6.sin6_port); - break; - default: - sport = -1; - } - } else { - sport = -1; - } + struct sock *sk = sock->sk; + + if (!sk) + return -1; - return sport; + return ntohs(READ_ONCE(inet_sk(sk)->inet_dport)); } /* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the -- 2.53.0