From: Frank Rowand <frank.row...@sony.com>
The Devicetree standard specifies an 8 byte alignment of the FDT.
Code in libfdt expects this alignment for an FDT image in memory.
kmemdup() returns 4 byte alignment on openrisc. Replace kmemdup()
with kmalloc(), align pointer, memcpy() to get proper alignment.
The 4 byte alignment exposed a related bug which triggered a crash
on openrisc with:
commit 79edff12060f ("scripts/dtc: Update to upstream version
v1.6.0-51-g183df9e9c2b9")
as reported in:
https://lore.kernel.org/lkml/20210327224116.69309-1-li...@roeck-us.net/
Reported-by: Guenter Roeck <li...@roeck-us.net>
Signed-off-by: Frank Rowand <frank.row...@sony.com>
---
changes since version 1:
- use pointer from kmalloc() for kfree() instead of using pointer that
has been modified for FDT alignment
changes since version 2:
- version 1 was a work in progress version, I failed to commit the following
final changes
- reorder first two arguments of of_overlay_apply()
changes since version 3:
- size of memory allocation and size of copy after pointer alignment
differ, use separate variables with correct values for each case
- edit comment to more clearly describe that ovcs->fdt is the allocated
memory region, which may be different than where the aligned pointer points
- remove unused parameter from of_overlay_apply()
drivers/of/of_private.h | 2 ++
drivers/of/overlay.c | 27 +++++++++++++++++----------
drivers/of/unittest.c | 13 ++++++++++---
3 files changed, 29 insertions(+), 13 deletions(-)
diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
index d9e6a324de0a..d717efbd637d 100644
--- a/drivers/of/of_private.h
+++ b/drivers/of/of_private.h
@@ -8,6 +8,8 @@
* Copyright (C) 1996-2005 Paul Mackerras.
*/
+#define FDT_ALIGN_SIZE 8
+
/**
* struct alias_prop - Alias property in 'aliases' node
* @link: List node to link the structure in aliases_lookup list
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 50bbe0edf538..ecf967c57900 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -57,7 +57,7 @@ struct fragment {
* struct overlay_changeset
* @id: changeset identifier
* @ovcs_list: list on which we are located
- * @fdt: FDT that was unflattened to create @overlay_tree
+ * @fdt: base of memory allocated to hold aligned FDT that was
unflattened to create @overlay_tree
* @overlay_tree: expanded device tree that contains the fragment nodes
* @count: count of fragment structures
* @fragments: fragment nodes in the overlay expanded device tree
@@ -719,8 +719,8 @@ static struct device_node *find_target(struct device_node
*info_node)
/**
* init_overlay_changeset() - initialize overlay changeset from overlay tree
* @ovcs: Overlay changeset to build
- * @fdt: the FDT that was unflattened to create @tree
- * @tree: Contains all the overlay fragments and overlay fixup nodes
+ * @fdt: base of memory allocated to hold aligned FDT that was
unflattened to create @tree
+ * @tree: Contains the overlay fragments and overlay fixup nodes
*
* Initialize @ovcs. Populate @ovcs->fragments with node information from
* the top level of @tree. The relevant top level nodes are the fragment
@@ -873,7 +873,7 @@ static void free_overlay_changeset(struct overlay_changeset
*ovcs)
* internal documentation
*
* of_overlay_apply() - Create and apply an overlay changeset
- * @fdt: the FDT that was unflattened to create @tree
+ * @fdt: base of memory allocated to hold the aligned FDT
* @tree: Expanded overlay device tree
* @ovcs_id: Pointer to overlay changeset id
*
@@ -913,7 +913,7 @@ static void free_overlay_changeset(struct overlay_changeset
*ovcs)
*/
static int of_overlay_apply(const void *fdt, struct device_node *tree,
- int *ovcs_id)
+ int *ovcs_id)
{
struct overlay_changeset *ovcs;
int ret = 0, ret_revert, ret_tmp;
@@ -953,7 +953,9 @@ static int of_overlay_apply(const void *fdt, struct
device_node *tree,
/*
* after overlay_notify(), ovcs->overlay_tree related pointers may have
* leaked to drivers, so can not kfree() tree, aka ovcs->overlay_tree;
- * and can not free fdt, aka ovcs->fdt
+ * and can not free memory containing aligned fdt. The aligned fdt
+ * is contained within the memory at ovcs->fdt, possibly at an offset
+ * from ovcs->fdt.
*/
ret = overlay_notify(ovcs, OF_OVERLAY_PRE_APPLY);
if (ret) {
@@ -1014,9 +1016,10 @@ static int of_overlay_apply(const void *fdt, struct
device_node *tree,
int of_overlay_fdt_apply(const void *overlay_fdt, u32 overlay_fdt_size,
int *ovcs_id)
{
- const void *new_fdt;
+ void *new_fdt;
+ void *new_fdt_align;
int ret;
- u32 size;
+ u32 size, size_alloc;
struct device_node *overlay_root;
*ovcs_id = 0;
@@ -1036,11 +1039,15 @@ int of_overlay_fdt_apply(const void *overlay_fdt, u32
overlay_fdt_size,
* Must create permanent copy of FDT because of_fdt_unflatten_tree()
* will create pointers to the passed in FDT in the unflattened tree.
*/
- new_fdt = kmemdup(overlay_fdt, size, GFP_KERNEL);
+ size_alloc = size + FDT_ALIGN_SIZE;
+ new_fdt = kmalloc(size_alloc, GFP_KERNEL);
if (!new_fdt)
return -ENOMEM;
- of_fdt_unflatten_tree(new_fdt, NULL, &overlay_root);
+ new_fdt_align = PTR_ALIGN(new_fdt, FDT_ALIGN_SIZE);
+ memcpy(new_fdt_align, overlay_fdt, size);
+
+ of_fdt_unflatten_tree(new_fdt_align, NULL, &overlay_root);
if (!overlay_root) {
pr_err("unable to unflatten overlay_fdt\n");
ret = -EINVAL;
diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
index eb100627c186..b43a86cc2068 100644
--- a/drivers/of/unittest.c
+++ b/drivers/of/unittest.c
@@ -22,6 +22,7 @@
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/platform_device.h>
+#include <linux/kernel.h>
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
@@ -1408,6 +1409,7 @@ static void attach_node_and_children(struct device_node
*np)
static int __init unittest_data_add(void)
{
void *unittest_data;
+ void *unittest_data_align;
struct device_node *unittest_data_node, *np;
/*
* __dtb_testcases_begin[] and __dtb_testcases_end[] are magically
@@ -1415,7 +1417,8 @@ static int __init unittest_data_add(void)
*/
extern uint8_t __dtb_testcases_begin[];
extern uint8_t __dtb_testcases_end[];
- const int size = __dtb_testcases_end - __dtb_testcases_begin;
+ u32 size = __dtb_testcases_end - __dtb_testcases_begin;
+ u32 size_alloc;
int rc;
if (!size) {
@@ -1425,11 +1428,15 @@ static int __init unittest_data_add(void)
}
/* creating copy */
- unittest_data = kmemdup(__dtb_testcases_begin, size, GFP_KERNEL);
+ size_alloc = size + FDT_ALIGN_SIZE;
+ unittest_data = kmalloc(size_alloc, GFP_KERNEL);
if (!unittest_data)
return -ENOMEM;
- of_fdt_unflatten_tree(unittest_data, NULL, &unittest_data_node);
+ unittest_data_align = PTR_ALIGN(unittest_data, FDT_ALIGN_SIZE);
+ memcpy(unittest_data_align, __dtb_testcases_begin, size);
+
+ of_fdt_unflatten_tree(unittest_data_align, NULL, &unittest_data_node);
if (!unittest_data_node) {
pr_warn("%s: No tree to attach; not running tests\n", __func__);
kfree(unittest_data);
--
Frank Rowand <frank.row...@sony.com>
