On 02/10/17 14:59, Linus Walleij wrote:
> I forgot to account for the fact that the device core holds a
> reference to a device added with device_initialize() that need
> to be released with a corresponding put_device() to reach a 0
> refcount at the end of the lifecycle.
>
> This led to a NULL pointer reference when freeing the device
> when e.g. unbidning the host device in sysfs.
>
> Fix this and use the device .release() callback to free the
> IDA and free:ing the memory used by the RPMB device.
>
> Before this patch:
>
> /sys/bus/amba/drivers/mmci-pl18x$ echo 80114000.sdi4_per2 > unbind
> [ 29.797332] mmc3: card 0001 removed
> [ 29.810791] Unable to handle kernel NULL pointer dereference at
> virtual address 00000050
> [ 29.818878] pgd = de70c000
> [ 29.821624] [00000050] *pgd=1e70a831, *pte=00000000, *ppte=00000000
> [ 29.827911] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
> [ 29.833282] Modules linked in:
> [ 29.836334] CPU: 1 PID: 154 Comm: sh Not tainted
> 4.14.0-rc3-00039-g83318e309566-dirty #736
> [ 29.844604] Hardware name: ST-Ericsson Ux5x0 platform (Device Tree Support)
> [ 29.851562] task: de572700 task.stack: de742000
> [ 29.856079] PC is at kernfs_find_ns+0x8/0x100
> [ 29.860443] LR is at kernfs_find_and_get_ns+0x30/0x48
>
> After this patch:
>
> /sys/bus/amba/drivers/mmci-pl18x$ echo 80005000.sdi4_per2 > unbind
> [ 20.623382] mmc3: card 0001 removed
> [ 20.627288] mmc_rpmb mmcblk3rpmb: removed
>
> Fixes: 0ab0c7c0e65a ("mmc: block: Convert RPMB to a character device")
> Reported-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> drivers/mmc/core/block.c | 21 ++++++++++++++++++---
> 1 file changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index c29dbcec7c61..2033a71bacc3 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -2329,6 +2329,14 @@ static const struct file_operations mmc_rpmb_fileops = {
> #endif
> };
>
> +static void mmc_blk_rpmb_device_release(struct device *dev)
> +{
> + struct mmc_rpmb_data *rpmb = dev_get_drvdata(dev);
> +
> + dev_info(dev, "removed\n");
Do we really need this message?
> + ida_simple_remove(&mmc_rpmb_ida, rpmb->id);
> + kfree(rpmb);
> +}
>
> static int mmc_blk_alloc_rpmb_part(struct mmc_card *card,
> struct mmc_blk_data *md,
> @@ -2371,6 +2379,8 @@ static int mmc_blk_alloc_rpmb_part(struct mmc_card *card,
> goto out_remove_ida;
> }
>
> + /* From this point, the .release() function cleans up the device */
> + rpmb->dev.release = mmc_blk_rpmb_device_release;
This should be before device_initialize(&rpmb->dev) then the error path
becomes just put_device(&rpmb->dev).
But further up is:
rpmb = kzalloc(sizeof(*rpmb), GFP_KERNEL);
if (!rpmb)
return -ENOMEM;
where it looks like you are leaking the ida.
> list_add(&rpmb->node, &md->rpmbs);
>
> string_get_size((u64)size, 512, STRING_UNITS_2,
> @@ -2384,17 +2394,22 @@ static int mmc_blk_alloc_rpmb_part(struct mmc_card *card,
> return 0;
>
> out_remove_ida:
> + put_device(&rpmb->dev);
> ida_simple_remove(&mmc_rpmb_ida, rpmb->id);
> kfree(rpmb);
> return ret;
> }
>
> static void mmc_blk_remove_rpmb_part(struct mmc_rpmb_data *rpmb)
> +
> {
> cdev_device_del(&rpmb->chrdev, &rpmb->dev);
> - device_del(&rpmb->dev);
> - ida_simple_remove(&mmc_rpmb_ida, rpmb->id);
> - kfree(rpmb);
> + /*
> + * Unless something is holding a reference to the device, this
> + * drops the last reference and triggers the device to cleanup
> + * and calls the .remove() callback.
> + */
This comment seems redundant since it is just describing how reference
counting works.
> + put_device(&rpmb->dev);
> }
>
> /* MMC Physical partitions consist of two boot partitions and
>
Also I noticed this function:
static int mmc_rpmb_chrdev_release(struct inode *inode, struct file *filp)
{
struct mmc_rpmb_data *rpmb = container_of(inode->i_cdev,
struct mmc_rpmb_data, chrdev);
put_device(&rpmb->dev);
mutex_lock(&open_lock);
rpmb->md->usage--;
mutex_unlock(&open_lock);
return 0;
}
What is going on with 'usage'? It looks weird.
What happens if you do this:
open the rpmb device
unbind the host controller
try to use an ioctl
close the rpmb device
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