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Wysocki" , Len Brown , linux-acpi@vger.kernel.org, Andi Shyti , Guenter Roeck , linux-hwmon@vger.kernel.org, MyungJoo Ham , Kyungmin Park , Chanwoo Choi Subject: [PATCH] mailbox/pcc.c move shmem unmap to teardown Date: Fri, 15 May 2026 12:10:01 -0400 Message-ID: <20260515161001.699470-1-admiyo@os.amperecomputing.com> X-Mailer: git-send-email 2.43.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: CY5PR15CA0050.namprd15.prod.outlook.com (2603:10b6:930:1b::16) To BN3PR01MB9212.prod.exchangelabs.com (2603:10b6:408:2cb::8) Precedence: bulk X-Mailing-List: linux-hwmon@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PR01MB9212:EE_|CH5PR01MB9032:EE_ X-MS-Office365-Filtering-Correlation-Id: 2c6702c5-6481-4530-0008-08deb29c6e4c X-MS-Exchange-AtpMessageProperties: SA X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|10070799003|7416014|1800799024|366016|55112099003|18002099003|56012099003|11063799003; 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If the shmem is torn down while the IRQ is active, a late interrupt can trigger a write to un-mapped memory. If the shmem is torn down after the IRQ, and another thread requests the channel again, we can end up with a channel that has had its shmem unmapped. By moving the unmap to the teardown process, we can let the mailbox mechanism prevent re-entrance into the startup/teardown functions. Assisted-by: Codex:gpt-5.4 Fixes: fa362ffafa51 ("mailbox: pcc: Always map the shared memory communication address") Signed-off-by: Adam Young --- drivers/mailbox/pcc.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c index 636879ae1db7..7fa2f6b5c492 100644 --- a/drivers/mailbox/pcc.c +++ b/drivers/mailbox/pcc.c @@ -401,18 +401,8 @@ EXPORT_SYMBOL_GPL(pcc_mbox_request_channel); void pcc_mbox_free_channel(struct pcc_mbox_chan *pchan) { struct mbox_chan *chan = pchan->mchan; - struct pcc_chan_info *pchan_info; - struct pcc_mbox_chan *pcc_mbox_chan; - if (!chan || !chan->cl) return; - pchan_info = chan->con_priv; - pcc_mbox_chan = &pchan_info->chan; - if (pcc_mbox_chan->shmem) { - iounmap(pcc_mbox_chan->shmem); - pcc_mbox_chan->shmem = NULL; - } - mbox_free_channel(chan); } EXPORT_SYMBOL_GPL(pcc_mbox_free_channel); @@ -488,15 +478,22 @@ static int pcc_startup(struct mbox_chan *chan) /** * pcc_shutdown - Called from Mailbox Controller code. Used here - * to free the interrupt. + * to free the interrupt and unmap the shared memory. * @chan: Pointer to Mailbox channel to shutdown. */ static void pcc_shutdown(struct mbox_chan *chan) { struct pcc_chan_info *pchan = chan->con_priv; + struct pcc_mbox_chan *pcc_mbox_chan; if (pchan->plat_irq > 0) devm_free_irq(chan->mbox->dev, pchan->plat_irq, chan); + + pcc_mbox_chan = &pchan->chan; + if (pcc_mbox_chan->shmem) { + iounmap(pcc_mbox_chan->shmem); + pcc_mbox_chan->shmem = NULL; + } } static const struct mbox_chan_ops pcc_chan_ops = { -- 2.43.0