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Commit f1a1171f authored by Jens Wiklander's avatar Jens Wiklander Committed by Lee Jones
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UPSTREAM: tee: handle lookup of shm with reference count 0 



commit dfd0743f1d9ea76931510ed150334d571fbab49d upstream.

Since the tee subsystem does not keep a strong reference to its idle
shared memory buffers, it races with other threads that try to destroy a
shared memory through a close of its dma-buf fd or by unmapping the
memory.

In tee_shm_get_from_id() when a lookup in teedev->idr has been
successful, it is possible that the tee_shm is in the dma-buf teardown
path, but that path is blocked by the teedev mutex. Since we don't have
an API to tell if the tee_shm is in the dma-buf teardown path or not we
must find another way of detecting this condition.

Fix this by doing the reference counting directly on the tee_shm using a
new refcount_t refcount field. dma-buf is replaced by using
anon_inode_getfd() instead, this separates the life-cycle of the
underlying file from the tee_shm. tee_shm_put() is updated to hold the
mutex when decreasing the refcount to 0 and then remove the tee_shm from
teedev->idr before releasing the mutex. This means that the tee_shm can
never be found unless it has a refcount larger than 0.

Fixes: 967c9cca ("tee: generic TEE subsystem")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: default avatarLars Persson <larper@axis.com>
Reviewed-by: default avatarSumit Garg <sumit.garg@linaro.org>
Reported-by: default avatarPatrik Lantz <patrik.lantz@axis.com>
[JW: backport to 5.4-stable]
Signed-off-by: default avatarJens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
Change-Id: Ibd2809a225b167563c65faff4a44e56e23c2e97b
parent 693158f7

drivers/tee/tee_shm.c

+67 −110
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

/*

 * Copyright (c) 2015-2016, Linaro Limited

 * Copyright (c) 2015-2017, 2019-2021 Linaro Limited

 */

#include <linux/anon_inodes.h>

#include <linux/device.h>

#include <linux/dma-buf.h>

#include <linux/fdtable.h>

#include <linux/idr.h>

#include <linux/mm.h>

#include <linux/sched.h>

#include <linux/slab.h>

#include <linux/tee_drv.h>

#include "tee_private.h"



static void tee_shm_release(struct tee_shm *shm)

static void tee_shm_release(struct tee_device *teedev, struct tee_shm *shm)

{

	struct tee_device *teedev = shm->teedev;



	mutex_lock(&teedev->mutex);

	idr_remove(&teedev->idr, shm->id);

	if (shm->ctx)

		list_del(&shm->link);

	mutex_unlock(&teedev->mutex);



	if (shm->flags & TEE_SHM_POOL) {

		struct tee_shm_pool_mgr *poolm;
@@ -52,51 +44,6 @@ static void tee_shm_release(struct tee_shm *shm) 
	tee_device_put(teedev);

}



static struct sg_table *tee_shm_op_map_dma_buf(struct dma_buf_attachment

			*attach, enum dma_data_direction dir)

{

	return NULL;

}



static void tee_shm_op_unmap_dma_buf(struct dma_buf_attachment *attach,

				     struct sg_table *table,

				     enum dma_data_direction dir)

{

}



static void tee_shm_op_release(struct dma_buf *dmabuf)

{

	struct tee_shm *shm = dmabuf->priv;



	tee_shm_release(shm);

}



static void *tee_shm_op_map(struct dma_buf *dmabuf, unsigned long pgnum)

{

	return NULL;

}



static int tee_shm_op_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)

{

	struct tee_shm *shm = dmabuf->priv;

	size_t size = vma->vm_end - vma->vm_start;



	/* Refuse sharing shared memory provided by application */

	if (shm->flags & TEE_SHM_REGISTER)

		return -EINVAL;



	return remap_pfn_range(vma, vma->vm_start, shm->paddr >> PAGE_SHIFT,

			       size, vma->vm_page_prot);

}



static const struct dma_buf_ops tee_shm_dma_buf_ops = {

	.map_dma_buf = tee_shm_op_map_dma_buf,

	.unmap_dma_buf = tee_shm_op_unmap_dma_buf,

	.release = tee_shm_op_release,

	.map = tee_shm_op_map,

	.mmap = tee_shm_op_mmap,

};



static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx,

				       struct tee_device *teedev,

				       size_t size, u32 flags)
@@ -137,6 +84,7 @@ static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx, 
		goto err_dev_put;

	}



	refcount_set(&shm->refcount, 1);

	shm->flags = flags | TEE_SHM_POOL;

	shm->teedev = teedev;

	shm->ctx = ctx;
@@ -159,21 +107,6 @@ static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx, 
		goto err_pool_free;

	}



	if (flags & TEE_SHM_DMA_BUF) {

		DEFINE_DMA_BUF_EXPORT_INFO(exp_info);



		exp_info.ops = &tee_shm_dma_buf_ops;

		exp_info.size = shm->size;

		exp_info.flags = O_RDWR;

		exp_info.priv = shm;



		shm->dmabuf = dma_buf_export(&exp_info);

		if (IS_ERR(shm->dmabuf)) {

			ret = ERR_CAST(shm->dmabuf);

			goto err_rem;

		}

	}



	if (ctx) {

		teedev_ctx_get(ctx);

		mutex_lock(&teedev->mutex);
@@ -182,10 +115,6 @@ static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx, 
	}



	return shm;

err_rem:

	mutex_lock(&teedev->mutex);

	idr_remove(&teedev->idr, shm->id);

	mutex_unlock(&teedev->mutex);

err_pool_free:

	poolm->ops->free(poolm, shm);

err_kfree:
@@ -268,6 +197,7 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr, 
		goto err;

	}



	refcount_set(&shm->refcount, 1);

	shm->flags = flags | TEE_SHM_REGISTER;

	shm->teedev = teedev;

	shm->ctx = ctx;
@@ -309,22 +239,6 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr, 
		goto err;

	}



	if (flags & TEE_SHM_DMA_BUF) {

		DEFINE_DMA_BUF_EXPORT_INFO(exp_info);



		exp_info.ops = &tee_shm_dma_buf_ops;

		exp_info.size = shm->size;

		exp_info.flags = O_RDWR;

		exp_info.priv = shm;



		shm->dmabuf = dma_buf_export(&exp_info);

		if (IS_ERR(shm->dmabuf)) {

			ret = ERR_CAST(shm->dmabuf);

			teedev->desc->ops->shm_unregister(ctx, shm);

			goto err;

		}

	}



	mutex_lock(&teedev->mutex);

	list_add_tail(&shm->link, &ctx->list_shm);

	mutex_unlock(&teedev->mutex);
@@ -352,6 +266,35 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr, 
}

EXPORT_SYMBOL_GPL(tee_shm_register);



static int tee_shm_fop_release(struct inode *inode, struct file *filp)

{

	tee_shm_put(filp->private_data);

	return 0;

}



static int tee_shm_fop_mmap(struct file *filp, struct vm_area_struct *vma)

{

	struct tee_shm *shm = filp->private_data;

	size_t size = vma->vm_end - vma->vm_start;



	/* Refuse sharing shared memory provided by application */

	if (shm->flags & TEE_SHM_USER_MAPPED)

		return -EINVAL;



	/* check for overflowing the buffer's size */

	if (vma->vm_pgoff + vma_pages(vma) > shm->size >> PAGE_SHIFT)

		return -EINVAL;



	return remap_pfn_range(vma, vma->vm_start, shm->paddr >> PAGE_SHIFT,

			       size, vma->vm_page_prot);

}



static const struct file_operations tee_shm_fops = {

	.owner = THIS_MODULE,

	.release = tee_shm_fop_release,

	.mmap = tee_shm_fop_mmap,

};



/**

 * tee_shm_get_fd() - Increase reference count and return file descriptor

 * @shm:	Shared memory handle
@@ -364,10 +307,11 @@ int tee_shm_get_fd(struct tee_shm *shm) 
	if (!(shm->flags & TEE_SHM_DMA_BUF))

		return -EINVAL;



	get_dma_buf(shm->dmabuf);

	fd = dma_buf_fd(shm->dmabuf, O_CLOEXEC);

	/* matched by tee_shm_put() in tee_shm_op_release() */

	refcount_inc(&shm->refcount);

	fd = anon_inode_getfd("tee_shm", &tee_shm_fops, shm, O_RDWR);

	if (fd < 0)

		dma_buf_put(shm->dmabuf);

		tee_shm_put(shm);

	return fd;

}
@@ -377,17 +321,7 @@ int tee_shm_get_fd(struct tee_shm *shm) 
 */

void tee_shm_free(struct tee_shm *shm)

{

	/*

	 * dma_buf_put() decreases the dmabuf reference counter and will

	 * call tee_shm_release() when the last reference is gone.

	 *

	 * In the case of driver private memory we call tee_shm_release

	 * directly instead as it doesn't have a reference counter.

	 */

	if (shm->flags & TEE_SHM_DMA_BUF)

		dma_buf_put(shm->dmabuf);

	else

		tee_shm_release(shm);

	tee_shm_put(shm);

}

EXPORT_SYMBOL_GPL(tee_shm_free);
@@ -494,10 +428,15 @@ struct tee_shm *tee_shm_get_from_id(struct tee_context *ctx, int id) 
	teedev = ctx->teedev;

	mutex_lock(&teedev->mutex);

	shm = idr_find(&teedev->idr, id);

	/*

	 * If the tee_shm was found in the IDR it must have a refcount

	 * larger than 0 due to the guarantee in tee_shm_put() below. So

	 * it's safe to use refcount_inc().

	 */

	if (!shm || shm->ctx != ctx)

		shm = ERR_PTR(-EINVAL);

	else if (shm->flags & TEE_SHM_DMA_BUF)

		get_dma_buf(shm->dmabuf);

	else

		refcount_inc(&shm->refcount);

	mutex_unlock(&teedev->mutex);

	return shm;

}
@@ -509,7 +448,25 @@ EXPORT_SYMBOL_GPL(tee_shm_get_from_id); 
 */

void tee_shm_put(struct tee_shm *shm)

{

	if (shm->flags & TEE_SHM_DMA_BUF)

		dma_buf_put(shm->dmabuf);

	struct tee_device *teedev = shm->teedev;

	bool do_release = false;



	mutex_lock(&teedev->mutex);

	if (refcount_dec_and_test(&shm->refcount)) {

		/*

		 * refcount has reached 0, we must now remove it from the

		 * IDR before releasing the mutex. This will guarantee that

		 * the refcount_inc() in tee_shm_get_from_id() never starts

		 * from 0.

		 */

		idr_remove(&teedev->idr, shm->id);

		if (shm->ctx)

			list_del(&shm->link);

		do_release = true;

	}

	mutex_unlock(&teedev->mutex);



	if (do_release)

		tee_shm_release(teedev, shm);

}

EXPORT_SYMBOL_GPL(tee_shm_put);

include/linux/tee_drv.h

+2 −2
Original line number Diff line number Diff line
@@ -178,7 +178,7 @@ void tee_device_unregister(struct tee_device *teedev); 
 * @offset:	offset of buffer in user space

 * @pages:	locked pages from userspace

 * @num_pages:	number of locked pages

 * @dmabuf:	dmabuf used to for exporting to user space

 * @refcount:	reference counter

 * @flags:	defined by TEE_SHM_* in tee_drv.h

 * @id:		unique id of a shared memory object on this device

 *
@@ -195,7 +195,7 @@ struct tee_shm { 
	unsigned int offset;

	struct page **pages;

	size_t num_pages;

	struct dma_buf *dmabuf;

	refcount_t refcount;

	u32 flags;

	int id;

};