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    Subject[PATCH 5.7 123/265] dma-direct: check return value when encrypting or decrypting memory
    Date
    From: David Rientjes <rientjes@google.com>

    [ Upstream commit 56fccf21d1961a06e2a0c96ce446ebf036651062 ]

    __change_page_attr() can fail which will cause set_memory_encrypted() and
    set_memory_decrypted() to return non-zero.

    If the device requires unencrypted DMA memory and decryption fails, simply
    free the memory and fail.

    If attempting to re-encrypt in the failure path and that encryption fails,
    there is no alternative other than to leak the memory.

    Fixes: c10f07aa27da ("dma/direct: Handle force decryption for DMA coherent buffers in common code")
    Signed-off-by: David Rientjes <rientjes@google.com>
    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/dma/direct.c | 19 ++++++++++++++-----
    1 file changed, 14 insertions(+), 5 deletions(-)

    diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
    index 4e789c46ff0bf..98c445dcb308b 100644
    --- a/kernel/dma/direct.c
    +++ b/kernel/dma/direct.c
    @@ -124,6 +124,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
    {
    struct page *page;
    void *ret;
    + int err;

    if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
    dma_alloc_need_uncached(dev, attrs) &&
    @@ -176,8 +177,12 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
    }

    ret = page_address(page);
    - if (force_dma_unencrypted(dev))
    - set_memory_decrypted((unsigned long)ret, 1 << get_order(size));
    + if (force_dma_unencrypted(dev)) {
    + err = set_memory_decrypted((unsigned long)ret,
    + 1 << get_order(size));
    + if (err)
    + goto out_free_pages;
    + }

    memset(ret, 0, size);

    @@ -196,9 +201,13 @@ done:
    return ret;

    out_encrypt_pages:
    - if (force_dma_unencrypted(dev))
    - set_memory_encrypted((unsigned long)page_address(page),
    - 1 << get_order(size));
    + if (force_dma_unencrypted(dev)) {
    + err = set_memory_encrypted((unsigned long)page_address(page),
    + 1 << get_order(size));
    + /* If memory cannot be re-encrypted, it must be leaked */
    + if (err)
    + return NULL;
    + }
    out_free_pages:
    dma_free_contiguous(dev, page, size);
    return NULL;
    --
    2.25.1
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