lkml.org 
[lkml]   [2013]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3.12 012/212] staging: zsmalloc: Ensure handle is never 0 on success
Date
3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Olav Haugan <ohaugan@codeaurora.org>

commit 67296874eb1cc80317bf2a8fba22b494e21eb29b upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/zsmalloc/zsmalloc-main.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)

--- 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
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(stru
}

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,



\
 
 \ /
  Last update: 2013-12-03 08:01    [W:0.591 / U:0.268 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site