From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f49.google.com (mail-wm1-f49.google.com [209.85.128.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ADCA938423F for ; Fri, 15 May 2026 18:54:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.49 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778871271; cv=none; b=sc5cKXvwMqCk3DRImihu3n1QWRUbx3GpeRhA/lI1UW3K2knnj6n7+yWXoE6827XTMUGSmwHHegADJOLMI39lf8ht7gD0UTFFuhw7g11gAZAewqSud1G0yjuR9UqSxj3ZWDnoU0PXGouKWsk1c3UYnbhKFOhqdh6DRmHDsw/bcCI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778871271; c=relaxed/simple; bh=5eaIm7oQrXrv26FV2waWzgjgidPzic9XkF5iTxDoZAA=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=kBYWAFvI27IAYSj9kxFVnCN3tvsVZbGXfccgoICRfQwprMKpo8N/t+HioNxWcxo22ogvqzUu/w8z4cNdfiSgWIcxQdl9RHEAa7YDZJoRf+Ii9pdlCP3Onkpqs41t1vjjuP+v+HckwWHY1BqYMmS5vjIwzs2p5FhpqiDLusEeo8I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=YTN8QEiG; arc=none smtp.client-ip=209.85.128.49 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="YTN8QEiG" Received: by mail-wm1-f49.google.com with SMTP id 5b1f17b1804b1-4891ca4ce02so2705e9.1 for ; Fri, 15 May 2026 11:54:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1778871265; x=1779476065; darn=vger.kernel.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=PNFlWNxHBBoOTkz1i9JncC0yIj0DqDbA8cq/UI1Bf44=; b=YTN8QEiGHHdnprLQd4QF4cecW35GhQVlLJOKOfrlbUIpLU3YETnSZ7SAZ75pD4+xLU JE95jMSsbzu7tvXxTEblYm67ZGMfe/XDBqYu9l9KCvf94QEbwgn2mVSnf+QDmBdO6yUu /JOROf/9RRxy4kRG2d2LLjwPrLrWHvN98DT8Q3xowg5Z5J4Q3BrqkQT6/2faP8j/N7Ei Bkmoa7IdWTvOBsy91glQdiElDn7pmakZxbVgrfE5WsA1HFEnVXh9HICSaz3ZGAusL6aT x5ftNRrsF4nOV+5ATj3tUzsa8cqi5nQRNxo4u2VEaaPgDJlirOcYBlnOy7ES2iFNLF+o f8Ow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778871265; x=1779476065; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=PNFlWNxHBBoOTkz1i9JncC0yIj0DqDbA8cq/UI1Bf44=; b=JGqeO0CDxCS67fo81EHJwUCPXrT7JXpu+mnVDTeVr/Xws/yhs41aRNWQ2Z/Lct87Zs riV8UI7V28B/+BKdkXePpN6uPr+XonwUPMLBpqRC/DimhWQrQYq/OntONMzNAKv4+1VA utQh0FOTWtRn1zTa/X3xbFMX2rlN27t5q/Q6VniOYHzg5Di3e6yJilSNnWExXi6+NlTk 9UDyY+DyUeV/miWHlSoG35dxGuuO8DV9gvu9hZ99lYLdRE3ykrcZLvdO6RQdo+Orbav/ x0lug9y1JuvuJCZ4DaHTwcfi52D7HDdLP+52IJYQiqhiHctdaprjuUDi358Sa93QfCld eRaA== X-Forwarded-Encrypted: i=1; AFNElJ/FXS3v/lnCAboSs30zesZ2jUWJiZWHmIN0Lnzebe5Cz/jEgD/2Hyz9+e5TRZoyvimj5o9l5Qw=@vger.kernel.org X-Gm-Message-State: AOJu0YzwUW6DgvvN5MMY89RShaSpwpwVX7jNacgOo/Dfg++q9LS6D+Rv f2/hLiIfofwXWR1WnhBKVZVwxp4WuSX5H3IcqGlz6nHAoYZmTI5PwkdVY497Ed12nA== X-Gm-Gg: Acq92OGrmih8aeiwswK5/E8d6UyEjjSAg8hbDlDOKhfjYhy9bwlOibYbAfkDRPsv8mn gpgxXLgy4DGm60evj6mziesGErLzkfOAj74nK3UV8yeF3WDbJ0JaKMlmNUw6gJdSl+5KEtrs/Qb fYKgE+qgB9x1hKcWXq/kR6+tt11SzV7TKAKcUgC9cH5suE34Ot7MNx2pKIyvDn3M/ljazIctNgb PowMTQTu72cpUWOW+qq8ogmdLidjunzPHv/Dm1bXcMgLptXEa+VNKoDZA4bwILbeo9bsqNV8olS vuYwDyJIJHBaZYWy3fyojQ6cdOYaI75iduBUV8GgkgHPVh9hbuF5vA/QJ+ahUDTt9bPczjeBBnM Aszbuvi6YOKpPUcJJ1OLwvHxfZtVEIUoim6LpT5PF0gkluTo2X3sZQnYYJ86qkAcm+IHloOZQLc 7T866UuH7U5hBi3VD7GQdIfV8TQcBTUYVfVOzqBU/n5/sIMbd+o0KV+p+9Ht0mMw== X-Received: by 2002:a05:600c:605a:b0:48a:55dc:9c1e with SMTP id 5b1f17b1804b1-48ff4b2c3bfmr64135e9.10.1778871264521; Fri, 15 May 2026 11:54:24 -0700 (PDT) Received: from localhost ([2a00:79e0:288a:8:7481:4dac:8e80:6e9b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48febe79ce3sm20112695e9.31.2026.05.15.11.54.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 May 2026 11:54:24 -0700 (PDT) From: Jann Horn Date: Fri, 15 May 2026 20:54:09 +0200 Subject: [PATCH 2/3] af_unix: Simplify unix_stream_data_wait() Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260515-unix-recv-wait-v1-2-76adb5f063d5@google.com> References: <20260515-unix-recv-wait-v1-0-76adb5f063d5@google.com> In-Reply-To: <20260515-unix-recv-wait-v1-0-76adb5f063d5@google.com> To: Kuniyuki Iwashima , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: Hannes Frederic Sowa , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Jann Horn X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1778871255; l=4212; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=5eaIm7oQrXrv26FV2waWzgjgidPzic9XkF5iTxDoZAA=; b=6VwkbRKbXyM57UZcd+u9NRFFl6a2vqKgQ5vgB5wq6NdR+FNOk105mWuSrcOwz+9Bf2Z+LL7U7 XiNleUuhKGzCWlSfUq4kCilsFmjn9b9WtFSLwY6wfd01XIiUGPC3fl7 X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= The current implementation of unix_stream_data_wait() works like this: - unix_stream_read_generic() grabs locks - unix_stream_read_generic() determines that the read must block - unix_stream_read_generic() drops locks - unix_stream_data_wait() sets up a wait_queue_entry - unix_stream_data_wait() rechecks that the read must still block, with less locking protection than unix_stream_read_generic() - unix_stream_data_wait() waits, then loops back to recheck again That seems needlessly complicated; and it also involves an ugly comparison between a potentially-dangling `last` pointer and another potentially-dangling `tail` pointer. Instead, let's set up a wait_queue_entry while the locks grabbed by unix_stream_read_generic() are still held, and after the wait, directly retry the read. Signed-off-by: Jann Horn --- net/unix/af_unix.c | 49 ++++++++++++++----------------------------------- 1 file changed, 14 insertions(+), 35 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index dc71ed79be4a..b38804e2c5ac 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2710,39 +2710,22 @@ static int unix_read_skb(struct sock *sk, skb_read_actor_t recv_actor) /* * Sleep until more data has arrived. But check for races.. */ -static long unix_stream_data_wait(struct sock *sk, long timeo, - struct sk_buff *last, bool freezable) +static long unix_stream_data_wait(struct sock *sk, long timeo, bool freezable) +__releases(&unix_sk(sk)->iolock) +__releases(&unix_sk(sk)->lock) { unsigned int state = TASK_INTERRUPTIBLE | freezable * TASK_FREEZABLE; - struct sk_buff *tail; DEFINE_WAIT(wait); - unix_state_lock(sk); - - for (;;) { - prepare_to_wait(sk_sleep(sk), &wait, state); - - tail = skb_peek_tail(&sk->sk_receive_queue); - if (tail != last || - sk->sk_err || - (sk->sk_shutdown & RCV_SHUTDOWN) || - signal_pending(current) || - !timeo) - break; - - sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk); - unix_state_unlock(sk); - timeo = schedule_timeout(timeo); - unix_state_lock(sk); - - if (sock_flag(sk, SOCK_DEAD)) - break; + prepare_to_wait(sk_sleep(sk), &wait, state); + unix_state_unlock(sk); + mutex_unlock(&unix_sk(sk)->iolock); - sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk); - } + sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk); + timeo = schedule_timeout(timeo); + sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk); finish_wait(sk_sleep(sk), &wait); - unix_state_unlock(sk); return timeo; } @@ -2955,7 +2938,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, skip = max(sk_peek_offset(sk, flags), 0); do { - struct sk_buff *skb, *last; + struct sk_buff *skb; int chunk; unix_state_lock(sk); @@ -2963,7 +2946,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, err = -ECONNRESET; goto unlock; } - last = skb = skb_peek(&sk->sk_receive_queue); + skb = skb_peek(&sk->sk_receive_queue); again: #if IS_ENABLED(CONFIG_AF_UNIX_OOB) @@ -2989,15 +2972,13 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, if (sk->sk_shutdown & RCV_SHUTDOWN) goto unlock; - unix_state_unlock(sk); if (!timeo) { err = -EAGAIN; - break; + goto unlock; } - mutex_unlock(&u->iolock); - - timeo = unix_stream_data_wait(sk, timeo, last, freezable); + /* does unix_state_unlock() and drops u->iolock */ + timeo = unix_stream_data_wait(sk, timeo, freezable); if (signal_pending(current)) { err = sock_intr_errno(timeo); @@ -3013,7 +2994,6 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, while (skip >= unix_skb_len(skb)) { skip -= unix_skb_len(skb); - last = skb; skb = skb_peek_next(skb, &sk->sk_receive_queue); if (!skb) goto again; @@ -3087,7 +3067,6 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state, break; skip = 0; - last = skb; unix_state_lock(sk); skb = skb_peek_next(skb, &sk->sk_receive_queue); if (skb) -- 2.54.0.563.g4f69b47b94-goog