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Subject[PATCH 4.14 45/62] mmc: block: Fix bug when removing RPMB chardev
Date
From: Linus Walleij <linus.walleij@linaro.org>

commit 1c87f73578497a6c3cc77bcbfd2e5bf15fe753c7 upstream.

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

Fixes: 97548575bef3 ("mmc: block: Convert RPMB to a character device")
Reported-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/mmc/core/block.c | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)

--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -2323,9 +2323,7 @@ static int mmc_rpmb_chrdev_open(struct i

get_device(&rpmb->dev);
filp->private_data = rpmb;
- mutex_lock(&open_lock);
- rpmb->md->usage++;
- mutex_unlock(&open_lock);
+ mmc_blk_get(rpmb->md->disk);

return nonseekable_open(inode, filp);
}
@@ -2336,9 +2334,7 @@ static int mmc_rpmb_chrdev_release(struc
struct mmc_rpmb_data, chrdev);

put_device(&rpmb->dev);
- mutex_lock(&open_lock);
- rpmb->md->usage--;
- mutex_unlock(&open_lock);
+ mmc_blk_put(rpmb->md);

return 0;
}
@@ -2354,6 +2350,13 @@ static const struct file_operations mmc_
#endif
};

+static void mmc_blk_rpmb_device_release(struct device *dev)
+{
+ struct mmc_rpmb_data *rpmb = dev_get_drvdata(dev);
+
+ 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,
@@ -2372,8 +2375,10 @@ static int mmc_blk_alloc_rpmb_part(struc
return devidx;

rpmb = kzalloc(sizeof(*rpmb), GFP_KERNEL);
- if (!rpmb)
+ if (!rpmb) {
+ ida_simple_remove(&mmc_rpmb_ida, devidx);
return -ENOMEM;
+ }

snprintf(rpmb_name, sizeof(rpmb_name),
"mmcblk%u%s", card->host->index, subname ? subname : "");
@@ -2384,6 +2389,7 @@ static int mmc_blk_alloc_rpmb_part(struc
rpmb->dev.bus = &mmc_rpmb_bus_type;
rpmb->dev.devt = MKDEV(MAJOR(mmc_rpmb_devt), rpmb->id);
rpmb->dev.parent = &card->dev;
+ rpmb->dev.release = mmc_blk_rpmb_device_release;
device_initialize(&rpmb->dev);
dev_set_drvdata(&rpmb->dev, rpmb);
rpmb->md = md;
@@ -2393,7 +2399,7 @@ static int mmc_blk_alloc_rpmb_part(struc
ret = cdev_device_add(&rpmb->chrdev, &rpmb->dev);
if (ret) {
pr_err("%s: could not add character device\n", rpmb_name);
- goto out_remove_ida;
+ goto out_put_device;
}

list_add(&rpmb->node, &md->rpmbs);
@@ -2408,18 +2414,16 @@ static int mmc_blk_alloc_rpmb_part(struc

return 0;

-out_remove_ida:
- ida_simple_remove(&mmc_rpmb_ida, rpmb->id);
- kfree(rpmb);
+out_put_device:
+ put_device(&rpmb->dev);
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);
+ put_device(&rpmb->dev);
}

/* MMC Physical partitions consist of two boot partitions and

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