From nobody Sun May 24 21:37:37 2026 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 93D5F36827E for ; Thu, 21 May 2026 09:04:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779354281; cv=none; b=aju+gK04isDFeASwLZl+/mBmDhCvj0byw0QkgD6Wm2kyZFWW5sjHz3U19ZUCzF7AjD7qaZIbALo55BauSut5ifms6kTKj76135MGRdKM4pR790V1QOzmHyR/jc8M2o78cJic1pZUTMorWM9gO3DzSAuvQF+5mVtVQVVDC5CfQ+Q= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779354281; c=relaxed/simple; bh=+dwTK0cuHhjwGvIjWknGmhW347ji5Nq6ak300K4ZR0U=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=WNoweNfsx12S/9Wxz7xML7dDp/r/tWQv+6onKfgvrSVp3DSRpGK/XtwFqSATGMDgJxkts6bfyKobcb+M1T2gS2gLiYOFsrt0J6X2bCsldzbUvlCyLmbt1bh5RD/ORZVFGXt+M3udXejo7trRzleOHa/zjyqVrDlXjC/m0MyCSkg= 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=J+7hS1gM; arc=none smtp.client-ip=209.85.214.202 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="J+7hS1gM" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2be9e0905a9so9423075ad.3 for ; Thu, 21 May 2026 02:04:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1779354279; x=1779959079; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=yAR4jGfkO1axcbCYTzSG39vOuVG5Rz/bo7M1T3CVqPQ=; b=J+7hS1gMA/KSRTV6KXRwLOSCmj0OBoeloMh7n4Ow0ilVQ/Ded8W3BF4b6eiLXa8oUJ 2fqXRe7qBARdr70uxmLsX083cJ7QhHaPxBI8Uo43RXmHm2cKKjzO6VDSXweUCVpwguPW o5boZLPvJ3YZY+bZj74Vp5UeYU3yoS+sgeVFwnLVTHPpB9UQ59d8pGAPdFwXhPqYPlih AxjY6+m7vPfAihWKZTlUyE+/jy0a+ziPZPkgtqkoGSPXY6AN4VtiX6ntCX94t/tk9m5f u6OtemoxD9+MmP1ZZDfmozsFYqmwrVsGD/+AT/b+FW9shZSNua7T1JhQ8UhtmiEVI9CW jw0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779354279; x=1779959079; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=yAR4jGfkO1axcbCYTzSG39vOuVG5Rz/bo7M1T3CVqPQ=; b=MqSEEO3gN0WmQu/oWeRFIe6uhmUi9F4RAsWaMQqeQpoYRlK7XycdU6g4TjG2E5Rz74 +rjprXh78Q+lrS0qvoNjxAehEf00AhorRlaTxiycxppYA8Xpc9v6X87NxSx/ahX5pSJ7 8j4ZNhYVSE++8jQ97h0qJxB0xBmrEF0Qkwg56svIb+C/KDqKR/1K2KupdQXLRshrS5Y6 D9rMRm16gP+ydKKbp8AOujnvy1pzgV8HlykEx/8AUvkc+chNC3sSd9IsoI6unvkpEJEi qxYbQqd0rqpc22Mccu8Ih+js4/urWEWlghhYDgYqZr70l6tQz4Vy9cNLYpcdcbOIN2Gk MK5A== X-Forwarded-Encrypted: i=1; AFNElJ/St9SPMG4PMgGkycQN4B8rtF1QHh9G0nh6MrZA4yiVRbqCITpnSpwhxvPhEhrQrY+2nQVxylL4iq12o68=@vger.kernel.org X-Gm-Message-State: AOJu0YxptjrWZB6i/NQJZQVulkldEMXy9f4QFBchjFA1dM+4BZGRXZ6c SIGki24plBGjcdgmRXf9C0UkJqBuMiBvt45zUh2UPwPIujbxWdE6qLIaKNLD9/C9boCw+cCn7EJ KOm+lMbLhexONjTCr3NQnz/vBDQ== X-Received: from pfblx15.prod.google.com ([2002:a05:6a00:754f:b0:82f:7833:9aa9]) (user=joonwonkang job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:3d1d:b0:3a2:ebfc:6bf3 with SMTP id adf61e73a8af0-3b30885a83cmr2492228637.29.1779354278650; Thu, 21 May 2026 02:04:38 -0700 (PDT) Date: Thu, 21 May 2026 09:04:31 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.54.0.746.g67dd491aae-goog Message-ID: <20260521090433.1353240-1-joonwonkang@google.com> Subject: [PATCH RESEND v6.12.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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jassi Brar commit c58e9456e30c ("mailbox: Fix NULL message support in mbox_send_messag= e()") 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=3Dtrue 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=3Dtrue 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 "!=3D NULL" check becomes "!=3D 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 --- 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 b4d52b814055..383c54d353ee 100644 --- a/drivers/mailbox/mailbox.c +++ b/drivers/mailbox/mailbox.c @@ -59,7 +59,7 @@ static void msg_submit(struct mbox_chan *chan) =20 spin_lock_irqsave(&chan->lock, flags); =20 - if (!chan->msg_count || chan->active_req) + if (!chan->msg_count || chan->active_req !=3D MBOX_NO_MSG) goto exit; =20 count =3D chan->msg_count; @@ -97,13 +97,13 @@ static void tx_tick(struct mbox_chan *chan, int r) =20 spin_lock_irqsave(&chan->lock, flags); mssg =3D chan->active_req; - chan->active_req =3D NULL; + chan->active_req =3D MBOX_NO_MSG; spin_unlock_irqrestore(&chan->lock, flags); =20 /* Submit next message */ msg_submit(chan); =20 - if (!mssg) + if (mssg =3D=3D MBOX_NO_MSG) return; =20 /* Notify the client */ @@ -125,7 +125,7 @@ static enum hrtimer_restart txdone_hrtimer(struct hrtim= er *hrtimer) for (i =3D 0; i < mbox->num_chans; i++) { struct mbox_chan *chan =3D &mbox->chans[i]; =20 - if (chan->active_req && chan->cl) { + if (chan->active_req !=3D MBOX_NO_MSG && chan->cl) { txdone =3D chan->mbox->ops->last_tx_done(chan); if (txdone) tx_tick(chan, 0); @@ -257,7 +257,7 @@ int mbox_send_message(struct mbox_chan *chan, void *mss= g) { int t; =20 - if (!chan || !chan->cl) + if (!chan || !chan->cl || mssg =3D=3D MBOX_NO_MSG) return -EINVAL; =20 t =3D add_to_rbuf(chan, mssg); @@ -331,7 +331,7 @@ static int __mbox_bind_client(struct mbox_chan *chan, s= truct mbox_client *cl) spin_lock_irqsave(&chan->lock, flags); chan->msg_free =3D 0; chan->msg_count =3D 0; - chan->active_req =3D NULL; + chan->active_req =3D MBOX_NO_MSG; chan->cl =3D cl; init_completion(&chan->tx_complete); =20 @@ -492,7 +492,7 @@ void mbox_free_channel(struct mbox_chan *chan) /* The queued TX requests are simply aborted, no callbacks are made */ spin_lock_irqsave(&chan->lock, flags); chan->cl =3D NULL; - chan->active_req =3D NULL; + chan->active_req =3D MBOX_NO_MSG; if (chan->txdone_method =3D=3D TXDONE_BY_ACK) chan->txdone_method =3D TXDONE_BY_POLL; =20 @@ -549,6 +549,7 @@ int mbox_controller_register(struct mbox_controller *mb= ox) =20 chan->cl =3D NULL; chan->mbox =3D mbox; + chan->active_req =3D MBOX_NO_MSG; chan->txdone_method =3D txdone; spin_lock_init(&chan->lock); } diff --git a/drivers/mailbox/tegra-hsp.c b/drivers/mailbox/tegra-hsp.c index 76f54f8b6b6c..8ef8b444de61 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 *ch= an, mbox_chan_txdone(chan, 0); =20 /* Wait until channel is empty */ - if (chan->active_req !=3D NULL) + if (chan->active_req !=3D MBOX_NO_MSG) continue; =20 return 0; diff --git a/include/linux/mailbox_controller.h b/include/linux/mailbox_con= troller.h index b91379922cb3..1689031c58c9 100644 --- a/include/linux/mailbox_controller.h +++ b/include/linux/mailbox_controller.h @@ -11,6 +11,9 @@ =20 struct mbox_chan; =20 +/* Sentinel value distinguishing "no active request" from "NULL message da= ta" */ +#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 --=20 2.54.0.746.g67dd491aae-goog