On 4/8/21 7:43 AM, frowand.list@xxxxxxxxx wrote:
> From: Frank Rowand <frank.rowand@xxxxxxxx>
>
> 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@xxxxxxxxxxxx/
>
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxx>
>
> ---
>
> Please review carefully, I am not yet fully awake...
>
> changes since version 1:
> - use pointer from kmalloc() for kfree() instead of using pointer that
> has been modified for FDT alignment
>
> 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
> +
Wasn't there a define for that elsewhere ?
> /**
> * 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..e0397d70d531 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_align: the FDT that was unflattened to create @tree, aligned
> + * @fdt: base of memory allocated to hold *@fdt_align
> * @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_align, const void *fdt,
> + struct device_node *tree, int *ovcs_id)
Is fdt_align used anywhere in this function ?
On a side note, it seems messy that of_overlay_apply() calls kfree on error.
That would probably be better handled in the calling code.
> {
> 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
fdt doesn't point to the aligned fdt, though. ovcs->fdt is the allocated fdt.
> */
> 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);
> +
size includes FDT_ALIGN_SIZE, so that copies beyond the end of the buffer
(or I am missing something).
> + 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_align, new_fdt, 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);
Unless I am missing something, this copies beyond the end of unittest_data
because FDT_ALIGN_SIZE was added to size. Maybe leave size alone and
allocate size + FDT_ALIGN_SIZE ?
Same as above, really.
> +
> + 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);
>
