[PATCH] mmc: atmel-mci: Fix use-after-free in atmci_remove due to race condition

[PATCH] mmc: atmel-mci: Fix use-after-free in atmci_remove due to race condition

[Pei Xiao]

In atmci_probe, &host->bh_work is bound with atmci_work_func, and
atmci_interrupt, atmci_timeout_timer and atmci_dma_complete can all
queue this work on system_bh_wq.

If we remove the module, atmci_remove makes cleanup and the memory
allocated for host with devm_kzalloc() is released after the remove
callback returns, while the work mentioned above may still be pending
or running. The sequence of operations that may lead to a UAF bug is
as follows:

CPU0                                      CPU1

                                          | atmci_interrupt
                                          | queue_work(system_bh_wq,
                                          |            &host->bh_work)
atmci_remove                              |
atmci_cleanup_slot(...)                   |
atmci_writel(host, ATMCI_IDR, ~0UL)       |
timer_delete_sync(&host->timer)           |
dma_release_channel(host->dma.chan)       |
free_irq(platform_get_irq(pdev, 0), host) |
                                          | atmci_work_func
                                          | // use host
// devm resources released after          |
// remove returns, host is freed          |
                                          | // use host (use-after-free)

Fix it by canceling the work after all the sources that can schedule
it (IRQ handler, timeout timer and DMA completion callback) have been
stopped, and before proceeding with the remaining cleanup in
atmci_remove.

Fixes: 7d2be0749a59 ("atmel-mci: Driver for Atmel on-chip MMC controllers")
Assisted-by: Codex:deepseek-v4-flash
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
---
 drivers/mmc/host/atmel-mci.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
index 3b4928f5b9b2..8f4df250a77a 100644
--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -2610,6 +2610,8 @@ static void atmci_remove(struct platform_device *pdev)
 
 	free_irq(platform_get_irq(pdev, 0), host);
 
+	cancel_work_sync(&host->bh_work);
+
 	clk_disable_unprepare(host->mck);
 
 	pm_runtime_disable(dev);
-- 
2.25.1

Re: [PATCH] mmc: atmel-mci: Fix use-after-free in atmci_remove due to race condition

[Ulf Hansson]

On Mon, Aug 3, 2026 at 11:48 AM Pei Xiao <xiaopei01@kylinos.cn> wrote:
>
> In atmci_probe, &host->bh_work is bound with atmci_work_func, and
> atmci_interrupt, atmci_timeout_timer and atmci_dma_complete can all
> queue this work on system_bh_wq.
>
> If we remove the module, atmci_remove makes cleanup and the memory
> allocated for host with devm_kzalloc() is released after the remove
> callback returns, while the work mentioned above may still be pending
> or running. The sequence of operations that may lead to a UAF bug is
> as follows:
>
> CPU0                                      CPU1
>
>                                           | atmci_interrupt
>                                           | queue_work(system_bh_wq,
>                                           |            &host->bh_work)
> atmci_remove                              |
> atmci_cleanup_slot(...)                   |
> atmci_writel(host, ATMCI_IDR, ~0UL)       |
> timer_delete_sync(&host->timer)           |
> dma_release_channel(host->dma.chan)       |
> free_irq(platform_get_irq(pdev, 0), host) |
>                                           | atmci_work_func
>                                           | // use host
> // devm resources released after          |
> // remove returns, host is freed          |
>                                           | // use host (use-after-free)
>
> Fix it by canceling the work after all the sources that can schedule
> it (IRQ handler, timeout timer and DMA completion callback) have been
> stopped, and before proceeding with the remaining cleanup in
> atmci_remove.
>
> Fixes: 7d2be0749a59 ("atmel-mci: Driver for Atmel on-chip MMC controllers")
> Assisted-by: Codex:deepseek-v4-flash
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

Applied for fixes and by adding a stable tag, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/atmel-mci.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
> index 3b4928f5b9b2..8f4df250a77a 100644
> --- a/drivers/mmc/host/atmel-mci.c
> +++ b/drivers/mmc/host/atmel-mci.c
> @@ -2610,6 +2610,8 @@ static void atmci_remove(struct platform_device *pdev)
>
>         free_irq(platform_get_irq(pdev, 0), host);
>
> +       cancel_work_sync(&host->bh_work);
> +
>         clk_disable_unprepare(host->mck);
>
>         pm_runtime_disable(dev);
> --
> 2.25.1
>

Re: [PATCH] mmc: atmel-mci: Fix use-after-free in atmci_remove due to race condition

[Aubin Constans]

On 03/08/2026 11:48, Pei Xiao wrote:

 > In atmci_probe, &host->bh_work is bound with atmci_work_func, and> atmci_interrupt, atmci_timeout_timer and atmci_dma_complete can all
> queue this work on system_bh_wq.
> 
> If we remove the module, atmci_remove makes cleanup and the memory
> allocated for host with devm_kzalloc() is released after the remove
> callback returns, while the work mentioned above may still be pending
> or running. The sequence of operations that may lead to a UAF bug is
> as follows:

Thank you for having spotted the issue, and sent this fix.
  >
> CPU0                                      CPU1
> 
>                                            | atmci_interrupt
>                                            | queue_work(system_bh_wq,
>                                            |            &host->bh_work)
> atmci_remove                              |
> atmci_cleanup_slot(...)                   |
> atmci_writel(host, ATMCI_IDR, ~0UL)       |
> timer_delete_sync(&host->timer)           |
> dma_release_channel(host->dma.chan)       |
> free_irq(platform_get_irq(pdev, 0), host) |
>                                            | atmci_work_func
>                                            | // use host
> // devm resources released after          |
> // remove returns, host is freed          |
>                                            | // use host (use-after-free)
> 
> Fix it by canceling the work after all the sources that can schedule
> it (IRQ handler, timeout timer and DMA completion callback) have been
> stopped, and before proceeding with the remaining cleanup in
> atmci_remove.

For completeness, PDC completion could be added to the above list of sources,
even though it is a subroutine of the IRQ handler.
PDC and DMA are exclusive.

Mentioning on which board or MPU the patch was tested would also be a welcome
addition.

> 
> Fixes: 7d2be0749a59 ("atmel-mci: Driver for Atmel on-chip MMC controllers")
> Assisted-by: Codex:deepseek-v4-flash
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
> ---
>   drivers/mmc/host/atmel-mci.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
> index 3b4928f5b9b2..8f4df250a77a 100644
> --- a/drivers/mmc/host/atmel-mci.c
> +++ b/drivers/mmc/host/atmel-mci.c
> @@ -2610,6 +2610,8 @@ static void atmci_remove(struct platform_device *pdev)
> 
>          free_irq(platform_get_irq(pdev, 0), host);
> 
> +       cancel_work_sync(&host->bh_work);
> +
>          clk_disable_unprepare(host->mck);
> 
>          pm_runtime_disable(dev);
> --
> 2.25.1
>