Re: [PATCH] crypto: ccp - fix SFS ioctl race against device teardown

[Thomas Huth <thuth@redhat.com>]

On 19/09/2026 21.24, Muhammad Bilal wrote:
> sfs_ioctl() reads psp_master->sfs_data and caches it in sfs_dev before
> taking sfs_ioctl_mutex, while sfs_dev_destroy() frees sfs_dev->page
> and sfs_dev->command_buf with no locking at all and only clears
> psp->sfs_data afterwards. A call to sfs_ioctl() that reads sfs_data
> just before sfs_dev_destroy() runs will still acquire the mutex and
> go on to use the now-freed command buffer in send_sfs_cmd().
> 
> Have both functions take sfs_ioctl_mutex before touching
> psp->sfs_data, so a call that is already using sfs_dev completes
> before teardown can free it, and a call arriving after teardown sees
> sfs_data cleared and returns -ENODEV instead of racing it.
> 
> Fixes: 648dbccc03a0 ("crypto: ccp - Add AMD Seamless Firmware Servicing (SFS) driver")
> Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
> ---
>   drivers/crypto/ccp/sfs.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sfs.c b/drivers/crypto/ccp/sfs.c
> index a4777839790b..530141f8bc74 100644
> --- a/drivers/crypto/ccp/sfs.c
> +++ b/drivers/crypto/ccp/sfs.c
> @@ -111,13 +111,13 @@ static long sfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>   	struct sfs_device *sfs_dev;
>   	int ret = 0;
>   
> +	guard(mutex)(&sfs_ioctl_mutex);
> +
>   	if (!psp_master || !psp_master->sfs_data)
>   		return -ENODEV;
>   
>   	sfs_dev = psp_master->sfs_data;
>   
> -	guard(mutex)(&sfs_ioctl_mutex);
> -
>   	switch (cmd) {
>   	case SFSIOCFWVERS:
>   		dev_dbg(sfs_dev->dev, "in SFSIOCFWVERS\n");
> @@ -191,8 +191,11 @@ static void sfs_exit(struct kref *ref)
>   
>   void sfs_dev_destroy(struct psp_device *psp)
>   {
> -	struct sfs_device *sfs_dev = psp->sfs_data;
> +	struct sfs_device *sfs_dev;
> +
> +	guard(mutex)(&sfs_ioctl_mutex);
>   
> +	sfs_dev = psp->sfs_data;
>   	if (!sfs_dev)
>   		return;
>   

Reviewed-by: Thomas Huth <thuth@redhat.com>