diff options
| author | Chuck Lever <chuck.lever@oracle.com> | 2026-05-25 12:51:18 -0400 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2026-05-28 13:35:31 +0200 |
| commit | 09dba37eee70d0596e26645015f1aa95a9848e9d (patch) | |
| tree | b54ea39d12dcbbbf2e25231af0df732842373ffc /net | |
| parent | 6b22d433aa13f68e3cd9534ca9a5f4277bfa01c2 (diff) | |
| download | linux-next-history-09dba37eee70d0596e26645015f1aa95a9848e9d.tar.gz | |
net/handshake: Take a long-lived file reference at submit
handshake_nl_accept_doit() needs the file pointer backing
req->hr_sk->sk_socket to survive the window between
handshake_req_next() and the subsequent FD_PREPARE() and get_file().
The submit-side sock_hold() does not provide that. sk_refcnt keeps
struct sock alive, but struct socket is owned by sock->file: when
the consumer fputs the last file reference, sock_release() tears
the socket down regardless of any sock_hold.
Add an hr_file pointer to struct handshake_req and acquire an
explicit reference on sock->file during handshake_req_submit().
handshake_complete() and handshake_req_cancel() release the
reference on the completion-bit-winning path.
The submit error path must also release the file reference, but
after rhashtable insertion a concurrent handshake_req_cancel() can
discover the request and race the error path. Gate the error-path
cleanup -- sk_destruct restoration, fput, and request destruction
-- with test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED), the same
serialization handshake_complete() and handshake_req_cancel()
already use. When cancel has already claimed ownership, the submit
error path returns without touching the request; socket teardown
handles final destruction.
The accept-side dereferences are not yet retargeted; that change
comes in the next patch.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://patch.msgid.link/20260525-handshake-file-pin-v3-4-66c616906ead@oracle.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net')
| -rw-r--r-- | net/handshake/handshake.h | 2 | ||||
| -rw-r--r-- | net/handshake/netlink.c | 6 | ||||
| -rw-r--r-- | net/handshake/request.c | 42 |
3 files changed, 37 insertions, 13 deletions
diff --git a/net/handshake/handshake.h b/net/handshake/handshake.h index 2289b0e274f40..da61cadd1ad3e 100644 --- a/net/handshake/handshake.h +++ b/net/handshake/handshake.h @@ -24,6 +24,7 @@ enum hn_flags_bits { HANDSHAKE_F_NET_DRAINING, }; +struct file; struct handshake_proto; /* One handshake request */ @@ -32,6 +33,7 @@ struct handshake_req { struct rhash_head hr_rhash; unsigned long hr_flags; const struct handshake_proto *hr_proto; + struct file *hr_file; struct sock *hr_sk; void (*hr_odestruct)(struct sock *sk); diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c index 039344979de93..1a5821eb71847 100644 --- a/net/handshake/netlink.c +++ b/net/handshake/netlink.c @@ -210,12 +210,6 @@ static void __net_exit handshake_net_exit(struct net *net) while (!list_empty(&requests)) { req = list_first_entry(&requests, struct handshake_req, hr_list); list_del(&req->hr_list); - - /* - * Requests on this list have not yet been - * accepted, so they do not have an fd to put. - */ - handshake_complete(req, -ETIMEDOUT, NULL); } } diff --git a/net/handshake/request.c b/net/handshake/request.c index 97f9f82399499..da064511ab860 100644 --- a/net/handshake/request.c +++ b/net/handshake/request.c @@ -13,6 +13,7 @@ #include <linux/module.h> #include <linux/skbuff.h> #include <linux/inet.h> +#include <linux/file.h> #include <linux/rhashtable.h> #include <net/sock.h> @@ -215,9 +216,16 @@ EXPORT_SYMBOL_IF_KUNIT(handshake_req_next); * A zero return value from handshake_req_submit() means that * exactly one subsequent completion callback is guaranteed. * - * A negative return value from handshake_req_submit() means that - * no completion callback will be done and that @req has been - * destroyed. + * A negative return value from handshake_req_submit() guarantees that + * no completion callback will occur and that @req is no longer owned by + * the caller. If cancellation wins the completion race after the request + * has been published, final destruction is deferred until socket teardown. + * + * The caller must hold a reference on @sock->file for the duration + * of this call. Once the request is published to the accept side, a + * concurrent completion or cancellation may release the request's pin on + * @sock->file; the caller's reference is what keeps @sock->sk valid until + * handshake_req_submit() returns. */ int handshake_req_submit(struct socket *sock, struct handshake_req *req, gfp_t flags) @@ -236,6 +244,14 @@ int handshake_req_submit(struct socket *sock, struct handshake_req *req, kfree(req); return -EINVAL; } + + /* + * Pin sock->file for the lifetime of the request so the + * accept side does not race a consumer that releases the + * socket while a handshake is pending. + */ + req->hr_file = get_file(sock->file); + req->hr_odestruct = req->hr_sk->sk_destruct; req->hr_sk->sk_destruct = handshake_sk_destruct; @@ -267,7 +283,11 @@ int handshake_req_submit(struct socket *sock, struct handshake_req *req, goto out_err; } - /* Prevent socket release while a handshake request is pending */ + /* + * Pin struct sock so sk_destruct does not run until the + * handshake completion path releases it; struct socket is + * held separately via hr_file above. + */ sock_hold(req->hr_sk); trace_handshake_submit(net, req, req->hr_sk); @@ -276,10 +296,13 @@ int handshake_req_submit(struct socket *sock, struct handshake_req *req, out_unlock: spin_unlock_bh(&hn->hn_lock); out_err: - /* Restore original destructor so socket teardown still runs on failure */ - req->hr_sk->sk_destruct = req->hr_odestruct; trace_handshake_submit_err(net, req, req->hr_sk, ret); - handshake_req_destroy(req); + if (!test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) { + /* Restore original destructor so socket teardown still runs. */ + req->hr_sk->sk_destruct = req->hr_odestruct; + fput(req->hr_file); + handshake_req_destroy(req); + } return ret; } EXPORT_SYMBOL(handshake_req_submit); @@ -291,11 +314,15 @@ void handshake_complete(struct handshake_req *req, int status, struct net *net = sock_net(sk); if (!test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) { + struct file *file = req->hr_file; + trace_handshake_complete(net, req, sk, status); req->hr_proto->hp_done(req, status, info); /* Handshake request is no longer pending */ sock_put(sk); + + fput(file); } } EXPORT_SYMBOL_IF_KUNIT(handshake_complete); @@ -344,6 +371,7 @@ out_true: /* Handshake request is no longer pending */ sock_put(sk); + fput(req->hr_file); return true; } EXPORT_SYMBOL(handshake_req_cancel); |