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Commit 67296874 authored by Olav Haugan's avatar Olav Haugan Committed by Greg Kroah-Hartman
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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: default avatarOlav Haugan <ohaugan@codeaurora.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b39f15c9

drivers/staging/zsmalloc/zsmalloc-main.c

+13 −4
Original line number Diff line number Diff line
@@ -430,7 +430,12 @@ static struct page *get_next_page(struct page *page) 
	return next;

}



/* Encode <page, obj_idx> as a single handle value */

/*

 * Encode <page, obj_idx> as a single handle value.

 * On hardware platforms with physical memory starting at 0x0 the pfn

 * could be 0 so we ensure that the handle will never be 0 by adjusting the

 * encoded obj_idx value before encoding.

 */

static void *obj_location_to_handle(struct page *page, unsigned long obj_idx)

{

	unsigned long handle;
@@ -441,17 +446,21 @@ static void *obj_location_to_handle(struct page *page, unsigned long obj_idx) 
	}



	handle = page_to_pfn(page) << OBJ_INDEX_BITS;

	handle |= (obj_idx & OBJ_INDEX_MASK);

	handle |= ((obj_idx + 1) & OBJ_INDEX_MASK);



	return (void *)handle;

}



/* Decode <page, obj_idx> pair from the given object handle */

/*

 * Decode <page, obj_idx> pair from the given object handle. We adjust the

 * decoded obj_idx back to its original value since it was adjusted in

 * obj_location_to_handle().

 */

static void obj_handle_to_location(unsigned long handle, struct page **page,

				unsigned long *obj_idx)

{

	*page = pfn_to_page(handle >> OBJ_INDEX_BITS);

	*obj_idx = handle & OBJ_INDEX_MASK;

	*obj_idx = (handle & OBJ_INDEX_MASK) - 1;

}



static unsigned long obj_idx_to_offset(struct page *page,