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: 967c9cca2cc5 ("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 --- drivers/tee/tee_shm.c | 177 +++++++++++++++------------------------- include/linux/tee_drv.h | 4 +- 2 files changed, 69 insertions(+), 112 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c index d6491e973fa4..0d5ae8053049 100644 --- a/drivers/tee/tee_shm.c +++ b/drivers/tee/tee_shm.c @@ -1,26 +1,18 @@ // 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); diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h index cd15c1b7fae0..e08ace76eba6 100644 --- a/include/linux/tee_drv.h +++ b/include/linux/tee_drv.h @@ -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; };