From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (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 947AC367B89 for ; Thu, 21 May 2026 09:04:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779354283; cv=none; b=ARZaQuS+S6tZpOuPcJ817vYM37BO+X8Z4uhqtAFKuOSKSCaQCCGqSiAE4qWh3PGLmJTisNknvAMZGreFcWemRfVwHGmVSjqZlUG37xQafinWBnIYUDx1+OTa45d85mhktDoQl1fvVLwwZaem40wI9UCra4UVRQXS8DnrcqIdbTk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779354283; c=relaxed/simple; bh=07NSKHICgCN3pWwcM2NlZ2C6aALUEOm7y9usKcSSRKQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=LWbAxNbwD+W9FXvj3zVufyo81fnYJIWySy0OTq2JPIbnTFQoeAYwUqV1qf0IU5BWYrJj5d9+XhFYnqiyB6G+tqxrYf/lpvw3FyaikeeeKUXu9Pc8WZwbKZGFdSDwpab8UmBqT7kSBSV9bH0ulJQfptU9zww4+QRbkLVUA3IkCvo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--joonwonkang.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=HVLaCFgQ; arc=none smtp.client-ip=209.85.210.202 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=flex--joonwonkang.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="HVLaCFgQ" Received: by mail-pf1-f202.google.com with SMTP id d2e1a72fcca58-8397b14a689so3931836b3a.2 for ; Thu, 21 May 2026 02:04:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1779354281; x=1779959081; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=CFeqTPO/75EomKS7CanmkqdMcPboUUUckwg42QFpRDY=; b=HVLaCFgQ5AStcp7yy4W38dml1KoMJX4Yq0IhWGckfP+26AxprMzB+Q7RlsPC8N+jgD 2w2D+e5zHjw1LcfDy6pzidRQO0WjV0sl7vr6tkmgebCZFyJBSb0eNIXFbxrq9knAAFNh t+P7yZC8rtxIZ+ff5A50cxdNreH/oHYhwXPfQWHEKii3AkrjS8mig/iqXm+EN9CVigVM BJQdQ2+nDzdOY6AfYvcj0WhRcRuvPL7ljYV9UzG49JnT9hIVyrXuoEael2+wHPS/ITGA k3fjreFjSmTSpzTHRGo7V3Wl89sd7a9J+E4Hxn72n+fAb9AxGxK9jswt9aAJHsRMV6dl N8Yg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779354281; x=1779959081; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=CFeqTPO/75EomKS7CanmkqdMcPboUUUckwg42QFpRDY=; b=OKLVRdxQ8oKNgdTuRrC/zMBKB3o1X4Fj6uRcm5Su8KeDcHQBcTr8DaGaZyC623IfFQ GOK/fUbdRNS6OeCDTgTx3fc/SyVP56tRF53X6kx93HFlOUO2h3+ZCKJ6L0NfkY70wz/7 7S5oCeO4JB2ifEW+tJSSYAz0/rCzB+JpsVLoE57T80A5J16SKMtLkLN5yiov/Yzd5Cva ZFCAEFeFDdHUZCkxhnReIkiupVAagp/XQJ+1LYG/280j5WORSnjsuTK2KfXZZLhRG153 EJCFzku40LQkkG26Q3Cw0owIY5/7aYpdV23OooMyTjBl3GpT2KDawR25r5VGih+7lkIR PkBQ== X-Forwarded-Encrypted: i=1; AFNElJ+hdx5k2rdYAa4UAI4b8uyMb86KiUhBrcuOxtOqXYyF62h22wQbCMdLOUdH53JOsnOMsEGkdnraVQEe@vger.kernel.org X-Gm-Message-State: AOJu0YzzauARjai1K/fa9s9jsPXdGuG6rmgoOUtt4NTmuPqNM1UQx65w JrPSKrk9h+TZlxlNLoAGI5nJnuB7KoPKc4LSSs8CuGLDdLM2wFW7K5YO3KtyiPGkVdXhy/JG6Tk YWhal0hMGTLFbiJPzmW43sttr3A== X-Received: from pfmm4.prod.google.com ([2002:a05:6a00:2484:b0:835:20c7:97df]) (user=joonwonkang job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:1908:b0:829:8cfb:df45 with SMTP id d2e1a72fcca58-8414acdd152mr2147460b3a.15.1779354280643; Thu, 21 May 2026 02:04:40 -0700 (PDT) Date: Thu, 21 May 2026 09:04:32 +0000 In-Reply-To: <20260521090433.1353240-1-joonwonkang@google.com> Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260521090433.1353240-1-joonwonkang@google.com> X-Mailer: git-send-email 2.54.0.746.g67dd491aae-goog Message-ID: <20260521090433.1353240-2-joonwonkang@google.com> Subject: [PATCH RESEND v2 v6.18.y] mailbox: Fix NULL message support in mbox_send_message() From: Joonwon Kang To: sashal@kernel.org, stable@vger.kernel.org, jassisinghbrar@gmail.com, greg@kroah.com Cc: thierry.reding@gmail.com, jonathanh@nvidia.com, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, joonwonkang@google.com, dianders@chromium.org, sudeep.holla@arm.com, linux-acpi@vger.kernel.org Content-Type: text/plain; charset="UTF-8" From: Jassi Brar commit c58e9456e30c ("mailbox: Fix NULL message support in mbox_send_message()") upstream. The active_req field serves double duty as both the "is a TX in flight" flag (NULL means idle) and the storage for the in-flight message pointer. When a client sends NULL via mbox_send_message(), active_req is set to NULL, which the framework misinterprets as "no active request". This breaks the TX state machine by: - tx_tick() short-circuits on (!mssg), skipping the tx_done callback and the tx_complete completion - txdone_hrtimer() skips the channel entirely since active_req is NULL, so poll-based TX-done detection never fires. Fix this by introducing a MBOX_NO_MSG sentinel value that means "no active request," freeing NULL to be valid message data. The sentinel is defined in the subsystem-internal mailbox.h so that controller drivers within drivers/mailbox/ can reference it, but it is not exposed to clients outside the subsystem. Fifteen in-tree callers send NULL (doorbell-style IPCs on Qualcomm, Tegra, TI, Xilinx, i.MX, SCMI, and PCC platforms). All were audited for regression: - Most already work around the bug via knows_txdone=true with a manual mbox_client_txdone() call, making the framework's tracking irrelevant. These are unaffected. - Poll-based callers (Xilinx zynqmp/r5) are strictly better off: the poll timer now correctly detects NULL-active channels instead of silently skipping them. - irq-qcom-mpm.c was a pre-existing bug -- the only Qualcomm caller that omitted the knows_txdone + mbox_client_txdone() pattern. Fixed in a companion commit ("irqchip/qcom-mpm: Fix missing mailbox TX done acknowledgment"). - No caller sets both a tx_done callback and sends NULL, nor combines tx_block=true with NULL sends, so the newly reachable callback/completion paths are never exercised. Also update tegra-hsp's flush callback, which directly inspects active_req to wait for the channel to drain: the old "!= NULL" check becomes "!= MBOX_NO_MSG", otherwise flush spins until timeout since the sentinel is non-NULL. The only tradeoff is that 'MBOX_NO_MSG' can not be used as a message by clients. Reported-by: Joonwon Kang Reviewed-by: Douglas Anderson Signed-off-by: Jassi Brar Signed-off-by: Joonwon Kang --- v2: Remove the obsolete change for drivers/mailbox/pcc.c. v1: Add the MBOX_NO_MSG check to drivers/mailbox/pcc.c. drivers/mailbox/mailbox.c | 15 ++++++++------- drivers/mailbox/tegra-hsp.c | 2 +- include/linux/mailbox_controller.h | 3 +++ 3 files changed, 12 insertions(+), 8 deletions(-) diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c index 617ba505691d..9622369cab66 100644 --- a/drivers/mailbox/mailbox.c +++ b/drivers/mailbox/mailbox.c @@ -52,7 +52,7 @@ static void msg_submit(struct mbox_chan *chan) int err = -EBUSY; scoped_guard(spinlock_irqsave, &chan->lock) { - if (!chan->msg_count || chan->active_req) + if (!chan->msg_count || chan->active_req != MBOX_NO_MSG) break; count = chan->msg_count; @@ -87,13 +87,13 @@ static void tx_tick(struct mbox_chan *chan, int r) scoped_guard(spinlock_irqsave, &chan->lock) { mssg = chan->active_req; - chan->active_req = NULL; + chan->active_req = MBOX_NO_MSG; } /* Submit next message */ msg_submit(chan); - if (!mssg) + if (mssg == MBOX_NO_MSG) return; /* Notify the client */ @@ -114,7 +114,7 @@ static enum hrtimer_restart txdone_hrtimer(struct hrtimer *hrtimer) for (i = 0; i < mbox->num_chans; i++) { struct mbox_chan *chan = &mbox->chans[i]; - if (chan->active_req && chan->cl) { + if (chan->active_req != MBOX_NO_MSG && chan->cl) { txdone = chan->mbox->ops->last_tx_done(chan); if (txdone) tx_tick(chan, 0); @@ -246,7 +246,7 @@ int mbox_send_message(struct mbox_chan *chan, void *mssg) { int t; - if (!chan || !chan->cl) + if (!chan || !chan->cl || mssg == MBOX_NO_MSG) return -EINVAL; t = add_to_rbuf(chan, mssg); @@ -319,7 +319,7 @@ static int __mbox_bind_client(struct mbox_chan *chan, struct mbox_client *cl) scoped_guard(spinlock_irqsave, &chan->lock) { chan->msg_free = 0; chan->msg_count = 0; - chan->active_req = NULL; + chan->active_req = MBOX_NO_MSG; chan->cl = cl; init_completion(&chan->tx_complete); @@ -477,7 +477,7 @@ void mbox_free_channel(struct mbox_chan *chan) /* The queued TX requests are simply aborted, no callbacks are made */ scoped_guard(spinlock_irqsave, &chan->lock) { chan->cl = NULL; - chan->active_req = NULL; + chan->active_req = MBOX_NO_MSG; if (chan->txdone_method == TXDONE_BY_ACK) chan->txdone_method = TXDONE_BY_POLL; } @@ -532,6 +532,7 @@ int mbox_controller_register(struct mbox_controller *mbox) chan->cl = NULL; chan->mbox = mbox; + chan->active_req = MBOX_NO_MSG; chan->txdone_method = txdone; spin_lock_init(&chan->lock); } diff --git a/drivers/mailbox/tegra-hsp.c b/drivers/mailbox/tegra-hsp.c index ed9a0bb2bcd8..7991e8dba579 100644 --- a/drivers/mailbox/tegra-hsp.c +++ b/drivers/mailbox/tegra-hsp.c @@ -497,7 +497,7 @@ static int tegra_hsp_mailbox_flush(struct mbox_chan *chan, mbox_chan_txdone(chan, 0); /* Wait until channel is empty */ - if (chan->active_req != NULL) + if (chan->active_req != MBOX_NO_MSG) continue; return 0; diff --git a/include/linux/mailbox_controller.h b/include/linux/mailbox_controller.h index 80a427c7ca29..1db0069c27c5 100644 --- a/include/linux/mailbox_controller.h +++ b/include/linux/mailbox_controller.h @@ -11,6 +11,9 @@ struct mbox_chan; +/* Sentinel value distinguishing "no active request" from "NULL message data" */ +#define MBOX_NO_MSG ((void *)-1) + /** * struct mbox_chan_ops - methods to control mailbox channels * @send_data: The API asks the MBOX controller driver, in atomic -- 2.54.0.746.g67dd491aae-goog