From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0D7BC36C0CE; Tue, 16 Jun 2026 16:36:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781627809; cv=none; b=HsUfS66CAITsYUy1LYsYKvBLpkvX2lK3IaF97LafHbE8axtYuzUjvq1C6Be8cNyqmKi/IgmUzE6vdG0uA2FTgfVIAfuqXKF4n/alyKAIWpjQsCjKxbwFy94Ur0+RZzj62Qf/EYuEa2PppcvBdkkzS01P7yb2zRQraqQMOHnLOkE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781627809; c=relaxed/simple; bh=ucyUCitAl/BhZgebN5lxozSaJ4j8qTZDWbKO6WHDxCE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Nw74/ghm0UJ4SXz8Wkt006g/M7BqGIQMZLj5hhksQIAid0g+0giQd/xvM/g5lrJhZAlyeb/Et9mibx2Z1IoAUqlACZik32JJFT2SCIQP/zS7S59bFaLdXbm2QBoWd/UchhcVOePs9N4m/Z9a2UkyI3TTC4IaxMCVnROKBQruhcQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ffzrX6Np; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ffzrX6Np" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1563F1F000E9; Tue, 16 Jun 2026 16:36:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781627808; bh=AAlB2Gad3a0gHbtjFdybtRxZR7Gl9SEazWzI22jBwZo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ffzrX6NpQ299BQWZ89SWSo/1XKc7DwgQqyJ9mlezyfNEixfhyG0pBZlkG6IzvPKTq x7su+4avXrBtY5X+1JzOteWpaX04zrOvw5ehWOeKoA9ZptpGbo4V/e0rzr/+7ncG0/ 4MO0HMBju0bhZVNnrXfDQhb/4zy/VFB7/Mg38vcI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Joonwon Kang , Douglas Anderson , Jassi Brar Subject: [PATCH 6.12 231/261] mailbox: Fix NULL message support in mbox_send_message() Date: Tue, 16 Jun 2026 20:31:09 +0530 Message-ID: <20260616145055.746623581@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145044.869532709@linuxfoundation.org> References: <20260616145044.869532709@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jassi Brar commit c58e9456e30c7098cbcd9f04571992be8a2e4e63 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 Signed-off-by: Greg Kroah-Hartman --- drivers/mailbox/mailbox.c | 15 ++++++++------- drivers/mailbox/tegra-hsp.c | 2 +- include/linux/mailbox_controller.h | 3 +++ 3 files changed, 12 insertions(+), 8 deletions(-) --- a/drivers/mailbox/mailbox.c +++ b/drivers/mailbox/mailbox.c @@ -59,7 +59,7 @@ static void msg_submit(struct mbox_chan spin_lock_irqsave(&chan->lock, flags); - if (!chan->msg_count || chan->active_req) + if (!chan->msg_count || chan->active_req != MBOX_NO_MSG) goto exit; count = chan->msg_count; @@ -97,13 +97,13 @@ static void tx_tick(struct mbox_chan *ch spin_lock_irqsave(&chan->lock, flags); mssg = chan->active_req; - chan->active_req = NULL; + chan->active_req = MBOX_NO_MSG; spin_unlock_irqrestore(&chan->lock, flags); /* Submit next message */ msg_submit(chan); - if (!mssg) + if (mssg == MBOX_NO_MSG) return; /* Notify the client */ @@ -125,7 +125,7 @@ static enum hrtimer_restart txdone_hrtim 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); @@ -257,7 +257,7 @@ int mbox_send_message(struct mbox_chan * { int t; - if (!chan || !chan->cl) + if (!chan || !chan->cl || mssg == MBOX_NO_MSG) return -EINVAL; t = add_to_rbuf(chan, mssg); @@ -331,7 +331,7 @@ static int __mbox_bind_client(struct mbo spin_lock_irqsave(&chan->lock, flags); 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); @@ -492,7 +492,7 @@ void mbox_free_channel(struct mbox_chan /* The queued TX requests are simply aborted, no callbacks are made */ spin_lock_irqsave(&chan->lock, flags); 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; @@ -548,6 +548,7 @@ int mbox_controller_register(struct mbox chan->cl = NULL; chan->mbox = mbox; + chan->active_req = MBOX_NO_MSG; chan->txdone_method = txdone; spin_lock_init(&chan->lock); } --- a/drivers/mailbox/tegra-hsp.c +++ b/drivers/mailbox/tegra-hsp.c @@ -497,7 +497,7 @@ static int tegra_hsp_mailbox_flush(struc 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; --- 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