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Date: Thu, 8 Apr 2021 15:06:27 -0500
From: Frank Rowand <frowand.list@...il.com>
To: Guenter Roeck <linux@...ck-us.net>,
Rob Herring <robh+dt@...nel.org>
Cc: Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
devicetree@...r.kernel.org,
Geert Uytterhoeven <geert+renesas@...der.be>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] of: unittest: overlay: ensure proper alignment of
copied FDT
Hi Guenter,
Thanks for the review!
On 4/8/21 10:32 AM, Guenter Roeck wrote:
> On 4/8/21 8:17 AM, frowand.list@...il.com wrote:
>> From: Frank Rowand <frank.rowand@...y.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-linux@roeck-us.net/
>>
>> Reported-by: Guenter Roeck <linux@...ck-us.net>
>> Signed-off-by: Frank Rowand <frank.rowand@...y.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()
>>
>> drivers/of/of_private.h | 2 ++
>> drivers/of/overlay.c | 28 +++++++++++++++++-----------
>> drivers/of/unittest.c | 12 +++++++++---
>> 3 files changed, 28 insertions(+), 14 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
>> +
>
> Use existing define ? Or was that local in libfdt ?
I don't see a define in libfdt. If anyone finds one,
I'll switch to it.
>
>> /**
>> * 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..cf770452e1e5 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 +873,8 @@ 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 *@..._align
>> + * @fdt_align: the FDT that was unflattened to create @tree, aligned
>> * @tree: Expanded overlay device tree
>> * @ovcs_id: Pointer to overlay changeset id
>> *
>> @@ -912,8 +913,8 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs)
>> * id is returned to *ovcs_id.
>> */
>>
>> -static int of_overlay_apply(const void *fdt, struct device_node *tree,
>> - int *ovcs_id)
>> +static int of_overlay_apply(const void *fdt, const void *fdt_align,
>
> fdt_align is not used in this function.
Thanks for catching that. Left over from earlier version where I
saved both aligned and unaligned addresses in init_overlay_changeset().
Will remove.
>
>> + struct device_node *tree, int *ovcs_id)
>> {
>> struct overlay_changeset *ovcs;
>> int ret = 0, ret_revert, ret_tmp;
>> @@ -953,7 +954,7 @@ 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, aka ovcs->fdt
>
> ovcs->fdt does not point to the aligned fdt, but to the allocated fdt.
Yes. The comment is not clear enough about that, I will modify.
>
>> */
>> ret = overlay_notify(ovcs, OF_OVERLAY_PRE_APPLY);
>> if (ret) {
>> @@ -1014,7 +1015,8 @@ 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;
>> struct device_node *overlay_root;
>> @@ -1036,18 +1038,22 @@ 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 += FDT_ALIGN_SIZE;
>> + new_fdt = kmalloc(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);
>
> Still copies beyond end of buffer.
Will fix with separate variables "size" and "size_alloc".
>
>> +
>> + of_fdt_unflatten_tree(new_fdt_align, NULL, &overlay_root);
>> if (!overlay_root) {
>> pr_err("unable to unflatten overlay_fdt\n");
>> ret = -EINVAL;
>> goto out_free_new_fdt;
>> }
>>
>> - ret = of_overlay_apply(new_fdt, overlay_root, ovcs_id);
>> + ret = of_overlay_apply(new_fdt, new_fdt_align, overlay_root, ovcs_id);
>> if (ret < 0) {
>> /*
>> * new_fdt and overlay_root now belong to the overlay
>> diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
>> index eb100627c186..29081a8b32e6 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 +1417,7 @@ 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;
>> int rc;
>>
>> if (!size) {
>> @@ -1425,11 +1427,15 @@ static int __init unittest_data_add(void)
>> }
>>
>> /* creating copy */
>> - unittest_data = kmemdup(__dtb_testcases_begin, size, GFP_KERNEL);
>> + size += FDT_ALIGN_SIZE;
>> + unittest_data = kmalloc(size, 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);
>
> Same as above.
Will fix with separate variables "size" and "size_alloc".
>
>> +
>> + 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);
>>
>
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