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of: unittest: overlay: ensure proper alignment of copied FDT

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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 79edff1206 ("scripts/dtc: Update to upstream version v1.6.0-51-g183df9e9c2b9")
as reported in:
https://lore.kernel.org/lkml/20210327224116.69309-1-linux@roeck-us.net/

Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Link: https://lore.kernel.org/r/20210408204508.2276230-1-frowand.list@gmail.com
Signed-off-by: Rob Herring <robh@kernel.org>
This commit is contained in:
Frank Rowand 2021-04-08 15:45:08 -05:00 committed by Rob Herring
parent 649cab56de
commit 48d499bd89
3 changed files with 23 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/of/of_private.h
View File

@ -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

22
drivers/of/overlay.c
View File

@ -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
*
@ -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) {
@ -1014,7 +1016,8 @@ out:
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;
struct device_node *overlay_root = NULL;
@ -1036,11 +1039,14 @@ 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);
new_fdt = kmalloc(size + FDT_ALIGN_SIZE, 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;

9
drivers/of/unittest.c
View File

@ -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 = NULL, *np;
/*
* __dtb_testcases_begin[] and __dtb_testcases_end[] are magically
@ -1425,11 +1427,14 @@ static int __init unittest_data_add(void)
}
/* creating copy */
unittest_data = kmemdup(__dtb_testcases_begin, size, GFP_KERNEL);
unittest_data = kmalloc(size + FDT_ALIGN_SIZE, GFP_KERNEL);
if (!unittest_data)
return -ENOMEM;
ret = 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);
ret = of_fdt_unflatten_tree(unittest_data_align, NULL, &unittest_data_node);
if (!ret) {
pr_warn("%s: unflatten testcases tree failed\n", __func__);
kfree(unittest_data);