From 67296874eb1cc80317bf2a8fba22b494e21eb29b Mon Sep 17 00:00:00 2001 From: Olav Haugan Date: Fri, 22 Nov 2013 09:30:41 -0800 Subject: [PATCH] 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 Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/staging/zsmalloc/zsmalloc-main.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c index 1a67537dbc56..3b950e5a918f 100644 --- a/drivers/staging/zsmalloc/zsmalloc-main.c +++ b/drivers/staging/zsmalloc/zsmalloc-main.c @@ -430,7 +430,12 @@ static struct page *get_next_page(struct page *page) return next; } -/* Encode as a single handle value */ +/* + * Encode 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 pair from the given object handle */ +/* + * Decode 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, -- 2.34.1