staging: zsmalloc: Ensure handle is never 0 on success
zsmalloc encodes a handle using the pfn and an object index. On hardware platforms with physical memory starting at 0x0 the pfn can be 0. This causes the encoded handle to be 0 and is incorrectly interpreted as an allocation failure. This issue affects all current and future SoCs with physical memory starting at 0x0. All MSM8974 SoCs which includes Google Nexus 5 devices are affected. To prevent this false error we ensure that the encoded handle will not be 0 when allocation succeeds. Signed-off-by: Olav Haugan <ohaugan@codeaurora.org> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -430,7 +430,12 @@ static struct page *get_next_page(struct page *page)
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return next;
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}
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/* Encode <page, obj_idx> as a single handle value */
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/*
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* Encode <page, obj_idx> as a single handle value.
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* On hardware platforms with physical memory starting at 0x0 the pfn
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* could be 0 so we ensure that the handle will never be 0 by adjusting the
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* encoded obj_idx value before encoding.
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*/
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static void *obj_location_to_handle(struct page *page, unsigned long obj_idx)
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{
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unsigned long handle;
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@ -441,17 +446,21 @@ static void *obj_location_to_handle(struct page *page, unsigned long obj_idx)
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}
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handle = page_to_pfn(page) << OBJ_INDEX_BITS;
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handle |= (obj_idx & OBJ_INDEX_MASK);
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handle |= ((obj_idx + 1) & OBJ_INDEX_MASK);
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return (void *)handle;
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}
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/* Decode <page, obj_idx> pair from the given object handle */
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/*
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* Decode <page, obj_idx> pair from the given object handle. We adjust the
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* decoded obj_idx back to its original value since it was adjusted in
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* obj_location_to_handle().
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*/
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static void obj_handle_to_location(unsigned long handle, struct page **page,
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unsigned long *obj_idx)
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{
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*page = pfn_to_page(handle >> OBJ_INDEX_BITS);
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*obj_idx = handle & OBJ_INDEX_MASK;
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*obj_idx = (handle & OBJ_INDEX_MASK) - 1;
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}
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static unsigned long obj_idx_to_offset(struct page *page,
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