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client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by CH1PEPF0000AD7B.mail.protection.outlook.com (10.167.244.58) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.339.3 via Frontend Transport; Sun, 16 Aug 2026 15:49:42 +0000 Received: from [127.0.1.1] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Sun, 16 Aug 2026 10:49:39 -0500 From: Shivank Garg Date: Sun, 16 Aug 2026 15:49:26 +0000 Subject: [PATCH v3 2/3] dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel() Precedence: bulk X-Mailing-List: linux-kernel@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: <20260816-dmaengine-kref-fix-v3-2-7e76187145df@amd.com> References: <20260816-dmaengine-kref-fix-v3-0-7e76187145df@amd.com> In-Reply-To: <20260816-dmaengine-kref-fix-v3-0-7e76187145df@amd.com> To: Vinod Koul , Frank Li , "Logan Gunthorpe" , Andrew Morton CC: , , , Shivank Garg , Sashiko X-Mailer: b4 0.15-dev-47d62 X-Developer-Signature: v=1; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: V6I1jsS6BYAOKQEdPwuBU5K322GRNAtnOTzW7hOj3Fq/dFoOv58F6PsbLxC9v9+79OBBH4BdJoS1ixtVG9fUYOYWTYVa6mpL7K0kCbrp/aNlKH5m4KsH+pu7bGRAGymPY59dm9afqB1gFiD3t4csBpwqwmHiXhAn2EdDUuIeHKgxABDaGhyoFfOB/zj3eRMf5BK3tVXNwNTyIm1LFtKOoZdyHSQ8xjxGBK8Yivayrxmp2MRUE7TosVrvxifgr9K8dsMAakBwNZj1nbajSWp4BuM2BKOxZQtbqw0a7/Ex8AQLmHLtLFhRUkgx/5Mc1kILeIO0gGo8hDPW8+mrwtofm4aMsG6JZ2GjNEr2a/3PW3rvW6m+cCgRA7Y7taXbjxXnCDIqC/J7cS1kNpZ1WlUgGIDbv8afCyrF+/+aWbIeb99j21zJBN2XMAexwSJ7Yc8M X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Aug 2026 15:49:42.0851 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f98d16b8-b1a1-4f34-9fbd-08defbadfcbd X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CH1PEPF0000AD7B.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB7149 When dma_device_put() drops the last reference on chan->device->ref, dma_device_release() runs and may free the dma_device along with its channels. Two paths still read that memory after the put: - dma_chan_put() reads chan->device->owner via dma_chan_to_owner() for the trailing module_put(). - dma_release_channel() calls dma_chan_put() before reading chan->slave, chan->name, chan->dev and chan->dbg_client_name. KASAN catches the first one: slab-use-after-free in dma_chan_put+0x3e6/0x4c0 Read of size 8 by task insmod/6319 Freed by task 6319: kfree+0x225/0x470 dma_chan_put+0x395/0x4c0 dmaengine_put+0xf8/0x160 Cache the module owner in dma_chan_put() before the put so the trailing module_put() does not need chan->device. In dma_release_channel(), move dma_chan_put() to the end, after every chan/device read. Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct") Suggested-by: Sashiko Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com Signed-off-by: Shivank Garg --- drivers/dma/dmaengine.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 516d6d933208..bf491eb10596 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -495,10 +495,13 @@ static int dma_chan_get(struct dma_chan *chan) */ static void dma_chan_put(struct dma_chan *chan) { + struct module *owner; + /* This channel is not in use, bail out */ if (!chan->client_count) return; + owner = dma_chan_to_owner(chan); chan->client_count--; /* This channel is not in use anymore, free it */ @@ -518,7 +521,7 @@ static void dma_chan_put(struct dma_chan *chan) /* This channel is not in use anymore, drop the device ref */ if (!chan->client_count) dma_device_put(chan->device); - module_put(dma_chan_to_owner(chan)); + module_put(owner); } enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie) @@ -916,8 +919,6 @@ void dma_release_channel(struct dma_chan *chan) if (--chan->device->privatecnt == 0) dma_cap_clear(DMA_PRIVATE, chan->device->cap_mask); - dma_chan_put(chan); - if (chan->slave) { sysfs_remove_link(&chan->dev->device.kobj, DMA_SLAVE_NAME); sysfs_remove_link(&chan->slave->kobj, chan->name); @@ -930,6 +931,7 @@ void dma_release_channel(struct dma_chan *chan) kfree(chan->dbg_client_name); chan->dbg_client_name = NULL; #endif + dma_chan_put(chan); mutex_unlock(&dma_list_mutex); } EXPORT_SYMBOL_GPL(dma_release_channel); -- 2.43.0