tls: Preserve sk_err across recvmsg() when data has been copied

JIRA: https://redhat.atlassian.net/browse/RHEL-152729

commit f508262ae9f21fe0e6c0749948b9dc7dd5a62a70
Author: Chuck Lever <chuck.lever@oracle.com>
Date:   Wed May 13 08:58:25 2026 -0400

    tls: Preserve sk_err across recvmsg() when data has been copied

    The sk_err check in tls_rx_rec_wait() consumes the error via
    sock_error(), which clears sk_err atomically. When the caller
    (tls_sw_recvmsg, tls_sw_splice_read, or tls_sw_read_sock) already
    has bytes copied to userspace, it returns those bytes and discards
    the error from this call. sk_err is now zero on the socket, so the
    next read syscall observes only RCV_SHUTDOWN and reports a clean
    EOF instead of the actual error (typically -ECONNRESET).

    The race is reachable when tls_read_flush_backlog()'s periodic
    sk_flush_backlog() triggers tcp_reset() in the middle of a
    multi-record read.

    Pass a has_copied flag to tls_rx_rec_wait(). When has_copied is
    false, consume sk_err via sock_error() as before. When has_copied
    is true, report the error from READ_ONCE() but leave sk_err set:
    the caller returns the byte count and discards the err from this
    call, and the next read syscall surfaces the preserved sk_err. This
    mirrors the tcp_recvmsg() preserve-and-surface pattern.

    The decrypt-abort path is unaffected: tls_err_abort() raises
    sk_err to EBADMSG after tls_rx_rec_wait() returns, and nothing
    on the caller's return path consumes it, so the EBADMSG surfaces
    on the next read.

    tls_sw_splice_read() passes has_copied=false: it processes
    one record per call, so no bytes have been copied within the
    function when tls_rx_rec_wait() runs. A reset that arrives
    between iterations of splice_direct_to_actor() (the sendfile()
    path) is still consumed by sock_error() in the later call, and the
    outer loop returns the prior iterations' byte count and drops the
    error. tcp_splice_read() exhibits the same pattern at the iteration
    boundary; addressing it belongs at the splice_direct_to_actor()
    layer and is out of scope here.

    Fixes: c46b01839f ("tls: rx: periodically flush socket backlog")
    Suggested-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
    Link: https://patch.msgid.link/20260513125825.205189-1-cel@kernel.org
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Sabrina Dubroca <sdubroca@redhat.com>

net/tls/tls_sw.c

@@ -1366,9 +1366,14 @@ unlock:
 	mutex_unlock(&tls_ctx->tx_lock);
 }
 
+/* When has_copied is true the caller has already moved bytes to
+ * userspace. Report sk_err but leave it set so the next read
+ * surfaces it instead of a spurious EOF, otherwise sk_err is
+ * consumed via sock_error().
+ */
 static int
 tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
-		bool released)
+		bool released, bool has_copied)
 {
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
 	struct tls_sw_context_rx *ctx = tls_sw_ctx_rx(tls_ctx);
@@ -1386,8 +1391,11 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
 		if (!sk_psock_queue_empty(psock))
 			return 0;
 
-		if (sk->sk_err)
+		if (sk->sk_err) {
+			if (has_copied)
+				return -READ_ONCE(sk->sk_err);
 			return sock_error(sk);
+		}
 
 		if (ret < 0)
 			return ret;
@@ -1423,7 +1431,7 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
 	}
 
 	if (unlikely(!tls_strp_msg_load(&ctx->strp, released)))
-		return tls_rx_rec_wait(sk, psock, nonblock, false);
+		return tls_rx_rec_wait(sk, psock, nonblock, false, has_copied);
 
 	return 1;
 }
@@ -2111,7 +2119,7 @@ int tls_sw_recvmsg(struct sock *sk,
 		int to_decrypt, chunk;
 
 		err = tls_rx_rec_wait(sk, psock, flags & MSG_DONTWAIT,
-				      released);
+				      released, !!(decrypted + copied));
 		if (err <= 0) {
 			if (psock) {
 				chunk = sk_msg_recvmsg(sk, psock, msg, len,
@@ -2298,7 +2306,7 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 		struct tls_decrypt_arg darg;
 
 		err = tls_rx_rec_wait(sk, NULL, flags & SPLICE_F_NONBLOCK,
-				      true);
+				      true, false);
 		if (err <= 0)
 			goto splice_read_end;
 
@@ -2384,7 +2392,7 @@ int tls_sw_read_sock(struct sock *sk, read_descriptor_t *desc,
 		} else {
 			struct tls_decrypt_arg darg;
 
-			err = tls_rx_rec_wait(sk, NULL, true, released);
+			err = tls_rx_rec_wait(sk, NULL, true, released, !!copied);
 			if (err <= 0)
 				goto read_sock_end;