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tee: handle lookup of shm with reference count 0
commitdfd0743f1d
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:967c9cca2c
("tee: generic TEE subsystem") Cc: stable@vger.kernel.org Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Lars Persson <larper@axis.com> Reviewed-by: Sumit Garg <sumit.garg@linaro.org> Reported-by: Patrik Lantz <patrik.lantz@axis.com> [JW: backport to 5.4-stable] Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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parent
4b38b12092
commit
940e68e57a
2 changed files with 69 additions and 112 deletions
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@ -1,26 +1,18 @@
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2015-2016, Linaro Limited
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* Copyright (c) 2015-2017, 2019-2021 Linaro Limited
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*/
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#include <linux/anon_inodes.h>
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#include <linux/device.h>
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#include <linux/dma-buf.h>
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#include <linux/fdtable.h>
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#include <linux/idr.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/tee_drv.h>
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#include "tee_private.h"
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static void tee_shm_release(struct tee_shm *shm)
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static void tee_shm_release(struct tee_device *teedev, struct tee_shm *shm)
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{
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struct tee_device *teedev = shm->teedev;
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mutex_lock(&teedev->mutex);
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idr_remove(&teedev->idr, shm->id);
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if (shm->ctx)
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list_del(&shm->link);
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mutex_unlock(&teedev->mutex);
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if (shm->flags & TEE_SHM_POOL) {
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struct tee_shm_pool_mgr *poolm;
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@ -52,51 +44,6 @@ static void tee_shm_release(struct tee_shm *shm)
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tee_device_put(teedev);
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}
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static struct sg_table *tee_shm_op_map_dma_buf(struct dma_buf_attachment
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*attach, enum dma_data_direction dir)
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{
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return NULL;
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}
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static void tee_shm_op_unmap_dma_buf(struct dma_buf_attachment *attach,
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struct sg_table *table,
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enum dma_data_direction dir)
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{
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}
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static void tee_shm_op_release(struct dma_buf *dmabuf)
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{
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struct tee_shm *shm = dmabuf->priv;
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tee_shm_release(shm);
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}
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static void *tee_shm_op_map(struct dma_buf *dmabuf, unsigned long pgnum)
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{
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return NULL;
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}
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static int tee_shm_op_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
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{
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struct tee_shm *shm = dmabuf->priv;
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size_t size = vma->vm_end - vma->vm_start;
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/* Refuse sharing shared memory provided by application */
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if (shm->flags & TEE_SHM_REGISTER)
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return -EINVAL;
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return remap_pfn_range(vma, vma->vm_start, shm->paddr >> PAGE_SHIFT,
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size, vma->vm_page_prot);
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}
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static const struct dma_buf_ops tee_shm_dma_buf_ops = {
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.map_dma_buf = tee_shm_op_map_dma_buf,
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.unmap_dma_buf = tee_shm_op_unmap_dma_buf,
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.release = tee_shm_op_release,
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.map = tee_shm_op_map,
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.mmap = tee_shm_op_mmap,
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};
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static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx,
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struct tee_device *teedev,
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size_t size, u32 flags)
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@ -137,6 +84,7 @@ static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx,
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goto err_dev_put;
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}
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refcount_set(&shm->refcount, 1);
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shm->flags = flags | TEE_SHM_POOL;
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shm->teedev = teedev;
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shm->ctx = ctx;
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@ -159,21 +107,6 @@ static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx,
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goto err_pool_free;
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}
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if (flags & TEE_SHM_DMA_BUF) {
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DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
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exp_info.ops = &tee_shm_dma_buf_ops;
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exp_info.size = shm->size;
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exp_info.flags = O_RDWR;
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exp_info.priv = shm;
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shm->dmabuf = dma_buf_export(&exp_info);
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if (IS_ERR(shm->dmabuf)) {
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ret = ERR_CAST(shm->dmabuf);
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goto err_rem;
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}
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}
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if (ctx) {
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teedev_ctx_get(ctx);
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mutex_lock(&teedev->mutex);
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@ -182,10 +115,6 @@ static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx,
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}
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return shm;
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err_rem:
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mutex_lock(&teedev->mutex);
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idr_remove(&teedev->idr, shm->id);
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mutex_unlock(&teedev->mutex);
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err_pool_free:
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poolm->ops->free(poolm, shm);
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err_kfree:
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@ -268,6 +197,7 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
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goto err;
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}
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refcount_set(&shm->refcount, 1);
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shm->flags = flags | TEE_SHM_REGISTER;
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shm->teedev = teedev;
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shm->ctx = ctx;
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@ -309,22 +239,6 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
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goto err;
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}
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if (flags & TEE_SHM_DMA_BUF) {
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DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
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exp_info.ops = &tee_shm_dma_buf_ops;
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exp_info.size = shm->size;
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exp_info.flags = O_RDWR;
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exp_info.priv = shm;
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shm->dmabuf = dma_buf_export(&exp_info);
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if (IS_ERR(shm->dmabuf)) {
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ret = ERR_CAST(shm->dmabuf);
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teedev->desc->ops->shm_unregister(ctx, shm);
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goto err;
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}
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}
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mutex_lock(&teedev->mutex);
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list_add_tail(&shm->link, &ctx->list_shm);
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mutex_unlock(&teedev->mutex);
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@ -352,6 +266,35 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
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}
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EXPORT_SYMBOL_GPL(tee_shm_register);
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static int tee_shm_fop_release(struct inode *inode, struct file *filp)
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{
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tee_shm_put(filp->private_data);
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return 0;
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}
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static int tee_shm_fop_mmap(struct file *filp, struct vm_area_struct *vma)
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{
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struct tee_shm *shm = filp->private_data;
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size_t size = vma->vm_end - vma->vm_start;
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/* Refuse sharing shared memory provided by application */
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if (shm->flags & TEE_SHM_USER_MAPPED)
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return -EINVAL;
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/* check for overflowing the buffer's size */
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if (vma->vm_pgoff + vma_pages(vma) > shm->size >> PAGE_SHIFT)
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return -EINVAL;
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return remap_pfn_range(vma, vma->vm_start, shm->paddr >> PAGE_SHIFT,
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size, vma->vm_page_prot);
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}
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static const struct file_operations tee_shm_fops = {
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.owner = THIS_MODULE,
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.release = tee_shm_fop_release,
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.mmap = tee_shm_fop_mmap,
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};
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/**
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* tee_shm_get_fd() - Increase reference count and return file descriptor
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* @shm: Shared memory handle
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if (!(shm->flags & TEE_SHM_DMA_BUF))
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return -EINVAL;
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get_dma_buf(shm->dmabuf);
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fd = dma_buf_fd(shm->dmabuf, O_CLOEXEC);
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/* matched by tee_shm_put() in tee_shm_op_release() */
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refcount_inc(&shm->refcount);
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fd = anon_inode_getfd("tee_shm", &tee_shm_fops, shm, O_RDWR);
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if (fd < 0)
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dma_buf_put(shm->dmabuf);
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tee_shm_put(shm);
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return fd;
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}
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@ -377,17 +321,7 @@ int tee_shm_get_fd(struct tee_shm *shm)
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*/
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void tee_shm_free(struct tee_shm *shm)
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{
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/*
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* dma_buf_put() decreases the dmabuf reference counter and will
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* call tee_shm_release() when the last reference is gone.
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*
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* In the case of driver private memory we call tee_shm_release
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* directly instead as it doesn't have a reference counter.
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*/
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if (shm->flags & TEE_SHM_DMA_BUF)
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dma_buf_put(shm->dmabuf);
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else
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tee_shm_release(shm);
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tee_shm_put(shm);
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}
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EXPORT_SYMBOL_GPL(tee_shm_free);
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teedev = ctx->teedev;
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mutex_lock(&teedev->mutex);
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shm = idr_find(&teedev->idr, id);
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/*
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* If the tee_shm was found in the IDR it must have a refcount
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* larger than 0 due to the guarantee in tee_shm_put() below. So
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* it's safe to use refcount_inc().
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*/
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if (!shm || shm->ctx != ctx)
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shm = ERR_PTR(-EINVAL);
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else if (shm->flags & TEE_SHM_DMA_BUF)
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get_dma_buf(shm->dmabuf);
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else
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refcount_inc(&shm->refcount);
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mutex_unlock(&teedev->mutex);
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return shm;
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}
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*/
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void tee_shm_put(struct tee_shm *shm)
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{
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if (shm->flags & TEE_SHM_DMA_BUF)
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dma_buf_put(shm->dmabuf);
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struct tee_device *teedev = shm->teedev;
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bool do_release = false;
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mutex_lock(&teedev->mutex);
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if (refcount_dec_and_test(&shm->refcount)) {
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/*
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* refcount has reached 0, we must now remove it from the
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* IDR before releasing the mutex. This will guarantee that
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* the refcount_inc() in tee_shm_get_from_id() never starts
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* from 0.
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*/
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idr_remove(&teedev->idr, shm->id);
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if (shm->ctx)
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list_del(&shm->link);
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do_release = true;
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}
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mutex_unlock(&teedev->mutex);
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if (do_release)
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tee_shm_release(teedev, shm);
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}
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EXPORT_SYMBOL_GPL(tee_shm_put);
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@ -178,7 +178,7 @@ void tee_device_unregister(struct tee_device *teedev);
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* @offset: offset of buffer in user space
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* @pages: locked pages from userspace
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* @num_pages: number of locked pages
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* @dmabuf: dmabuf used to for exporting to user space
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* @refcount: reference counter
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* @flags: defined by TEE_SHM_* in tee_drv.h
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* @id: unique id of a shared memory object on this device
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*
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@ -195,7 +195,7 @@ struct tee_shm {
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unsigned int offset;
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struct page **pages;
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size_t num_pages;
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struct dma_buf *dmabuf;
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refcount_t refcount;
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u32 flags;
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int id;
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};
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