From: Frank Li <Frank.li@oss.nxp.com>
To: "Ziyou Wang (Lenovo)" <ziyou.dev@gmail.com>
Cc: Vinod Koul <vkoul@kernel.org>,
Vinicius Costa Gomes <vinicius.gomes@intel.com>,
Dave Jiang <dave.jiang@intel.com>, Frank Li <Frank.Li@kernel.org>,
dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
Adrian Huang <adrianhuang0701@gmail.com>
Subject: Re: [PATCH] dmaengine: idxd: Fix use-after-free in idxd_remove
Date: Fri, 30 Oct 2026 09:54:05 -0500 [thread overview]
Message-ID: <auSvjQ8JKZ1GKWVT@SMW015318> (raw)
In-Reply-To: <20260911065547.161522-1-ziyou.dev@gmail.com>
On Fri, Sep 11, 2026 at 02:55:47PM +0800, Ziyou Wang (Lenovo) wrote:
> [You don't often get email from ziyou.dev@gmail.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>
> When unbinding the idxd driver, the following call trace is observed:
>
> general protection fault, probably for non-canonical address 0x18fc1d6937256657
> CPU: 117 UID: 0 PID: 3396 Comm: python3 Tainted: G E 7.2.0-rc5-latest+ #11 PREEMPT(lazy)
> Hardware name: Lenovo WenTian WR5220 G5, BIOS speb50m-2.54
> RIP: 0010:__refill_objects_node+0x2da/0x5e0
> Call Trace:
> <TASK>
> refill_objects+0x1ee/0x2e0
> __pcs_replace_empty_main+0x1e1/0x330
> __kmalloc_noprof+0x503/0x550
> ext4_htree_store_dirent+0x34/0x110 [ext4]
> htree_dirblock_to_tree+0x1a9/0x2c0 [ext4]
> ext4_htree_fill_tree+0x246/0x3d0 [ext4]
> ext4_readdir+0x863/0x9d0 [ext4]
> iterate_dir+0xa6/0x260
> __x64_sys_getdents64+0x76/0x130
> do_syscall_64+0x98/0x620
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
> </TASK>
>
> With the KASAN-enabled kernel, the kernel reports a use-after-free bug:
>
> idxd_unregister_devices() calls device_unregister(wq), which triggers
> the wq release callback and frees wq memory via kfree(). However,
> idxd->wqs[] array still holds the freed pointer. Later, when
> device_unregister(idxd) calls idxd_device_drv_remove(), it accesses
> wq->state through idxd->wqs[], resulting in use-after-free.
>
> The same issue exists for idxd->engines[] and idxd->groups[] arrays.
>
> KASAN report:
>
> BUG: KASAN: slab-use-after-free in idxd_device_drv_remove+0xc1/0x100 [idxd]
> Read of size 4 at addr ff1100038d296414 by task python3/3354
> CPU: 20 UID: 0 PID: 3354 Comm: python3 Tainted: G E 7.2.0-rc5-debug+
> Hardware name: Lenovo WenTian WR5220 G5, BIOS speb50m-2.54
>
> Call Trace:
> <TASK>
> dump_stack_lvl+0x5b/0x80
> print_report+0x153/0x4b5
> kasan_report+0xbc/0xf0
> idxd_device_drv_remove+0xc1/0x100 [idxd]
> device_release_driver_internal+0x244/0x2e0
> bus_remove_device+0x195/0x2b0
> device_del+0x24b/0x540
> device_unregister+0x17/0x80
> idxd_remove+0x3f/0x120 [idxd]
> pci_device_remove+0x6d/0xf0
> device_release_driver_internal+0x244/0x2e0
> unbind_store+0xae/0xb0
> kernfs_fop_write_iter+0x205/0x2d0
> vfs_write+0x3a9/0x6b0
> ksys_write+0xc7/0x160
> do_syscall_64+0x9c/0x620
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
> </TASK>
>
> Allocated by task 1219:
> kasan_save_stack+0x20/0x40
> kasan_save_track+0x14/0x30
> __kasan_kmalloc+0x9a/0xb0
> __kmalloc_cache_node_noprof+0x1c6/0x470
> idxd_pci_probe_alloc+0x103f/0x2430 [idxd]
> local_pci_probe+0x71/0xd0
> local_pci_probe_callback+0x20/0x40
> process_one_work+0x389/0x6a0
> worker_thread+0x321+0x590
> kthread+0x1b4/0x200
> ret_from_fork+0x3bd/0x4d0
> ret_from_fork_asm+0x1a/0x30
>
> Freed by task 3354:
> kasan_save_stack+0x20/0x40
> kasan_save_track+0x14/0x30
> kasan_save_free_info+0x3b/0x70
> __kasan_slab_free+0x6b/0x90
> kfree+0x1d4/0x520
> device_release+0x77/0x120
> kobject_put+0xdb/0x2a0
> idxd_unregister_devices+0x5b/0x130 [idxd]
> idxd_remove+0x2f/0x120 [idxd]
> pci_device_remove+0x6d/0xf0
> device_release_driver_internal+0x244/0x2e0
> unbind_store+0xae/0xb0
> kernfs_fop_write_iter+0x205/0x2d0
> vfs_write+0x3a9/0x6b0
> ksys_write+0xc7/0x160
> do_syscall_64+0x9c/0x620
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
Can you trim dump to make commit message short.
>
> Fix by taking refs on wq/engine/group conf_dev in idxd_unregister_devices()
> before calling device_unregister(). This prevents their memory from being
> freed until after idxd_device_drv_remove() completes. Add idxd_put_devices()
> to release the refs after all cleanup activities are done.
>
> To reproduce:
> cd dsa-perf-micros
> ./scripts/setup_dsa.sh -d dsa0 -w 1 -m s -e 4
> echo "0000:00:01.0" > /sys/bus/pci/drivers/idxd/unbind
This is typical unbind driver method. So needn't this paragraph.
Frank
>
> Fixes: 47c16ac27d4c ("dmaengine: idxd: fix idxd conf_dev 'struct device' lifetime")
> Suggested-by: Adrian Huang (Lenovo) <adrianhuang0701@gmail.com>
> Signed-off-by: Ziyou Wang (Lenovo) <ziyou.dev@gmail.com>
> ---
> Added a Suggested-by tag for Adrian, as he came up with the idea for this patch.
>
> drivers/dma/idxd/init.c | 15 +++++++++++++++
> drivers/dma/idxd/sysfs.c | 8 ++++++++
> 2 files changed, 23 insertions(+)
>
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index 4b827a329756..212efbfebacc 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -1263,6 +1263,20 @@ static void idxd_shutdown(struct pci_dev *pdev)
> flush_workqueue(idxd->wq);
> }
>
> +static void idxd_put_devices(struct idxd_device *idxd)
> +{
> + int i;
> +
> + for (i = 0; i < idxd->max_wqs; i++)
> + put_device(wq_confdev(idxd->wqs[i]));
> +
> + for (i = 0; i < idxd->max_engines; i++)
> + put_device(engine_confdev(idxd->engines[i]));
> +
> + for (i = 0; i < idxd->max_groups; i++)
> + put_device(group_confdev(idxd->groups[i]));
> +}
> +
> static void idxd_remove(struct pci_dev *pdev)
> {
> struct idxd_device *idxd = pci_get_drvdata(pdev);
> @@ -1284,6 +1298,7 @@ static void idxd_remove(struct pci_dev *pdev)
> if (device_pasid_enabled(idxd))
> idxd_disable_system_pasid(idxd);
> pci_iounmap(pdev, idxd->reg_base);
> + idxd_put_devices(idxd);
> put_device(idxd_confdev(idxd));
> pci_disable_device(pdev);
> }
> diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
> index 6d251095c350..eca96a4dcecd 100644
> --- a/drivers/dma/idxd/sysfs.c
> +++ b/drivers/dma/idxd/sysfs.c
> @@ -1988,21 +1988,29 @@ void idxd_unregister_devices(struct idxd_device *idxd)
> {
> int i;
>
> + /*
> + * Take a reference count to the idxd device to prevent the
> + * corresponding idxd context from being freed, as the driver
> + * still needs it for the remaining cleanup operations.
> + */
> for (i = 0; i < idxd->max_wqs; i++) {
> struct idxd_wq *wq = idxd->wqs[i];
>
> + get_device(wq_confdev(wq));
> device_unregister(wq_confdev(wq));
> }
>
> for (i = 0; i < idxd->max_engines; i++) {
> struct idxd_engine *engine = idxd->engines[i];
>
> + get_device(engine_confdev(engine));
> device_unregister(engine_confdev(engine));
> }
>
> for (i = 0; i < idxd->max_groups; i++) {
> struct idxd_group *group = idxd->groups[i];
>
> + get_device(group_confdev(group));
> device_unregister(group_confdev(group));
> }
> }
> --
> 2.53.0
>
next prev parent reply other threads:[~2026-10-30 14:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-11 6:55 [PATCH] dmaengine: idxd: Fix use-after-free in idxd_remove Ziyou Wang (Lenovo)
2026-09-11 7:14 ` sashiko-bot
2026-10-30 14:54 ` Frank Li [this message]
[not found] ` <CABBdrdLtTJL7-xgB4i=AvqBoBJfFzYvJe+gV+KyLz5=QjUWkCg@mail.gmail.com>
2026-10-31 0:13 ` Vinicius Costa Gomes
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