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SubjectRe: [PATCH] resource: fix an error which walks through iomem resources
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Please ignore this patch, i have put this patch into another patches series, you can
refer to the link below:

https://lore.kernel.org/patchwork/patch/988431/
https://lore.kernel.org/patchwork/patch/988432/
https://lore.kernel.org/patchwork/patch/988433/

Thanks.

在 2018年09月17日 14:20, Lianbo Jiang 写道:
> When we walk through iomem resources by calling walk_iomem_res_desc(), the
> values of the function parameter may be modified in the while loop of __walk
> _iomem_res_desc(), which will cause us to not get the desired result in some
> cases.
>
> At present, it only restores the original value of res->end, but it doesn't
> restore the original value of res->flags in the while loop of __walk_iomem
> _res_desc(). Whenever the find_next_iomem_res() finds a resource and returns
> the result, the original values of this resource will be modified, which might
> lead to an error in the next loop. For example:
>
> The original value of resource flags is: res->flags=0x80000200(initial value)
>
> p->flags _ 0x81000200 _ _ 0x80000200 _
> / \ / \
> |________|_______A________|____|_....._|______B_________|......___|
> 0 0xffffffff
> (memory address ranges)
>
> Note: if ((p->flags & res->flags) != res->flags) continue;
>
> When the resource A is found, the original value of this resource flags will
> be changed to 0x81000200(res->flags=0x81000200), and continue to look for the
> next resource, when the loop reaches resource B, it can not get the resource B
> any more(you can refer to the for loop of find_next_iomem_res()), because the
> value of conditional expression will become true and will also jump the resource
> B. In fact, we should get the resource A and B when we walk through the whole
> tree, but it only gets the resource A, the resource B is missed.
>
> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
> ---
> kernel/resource.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 30e1bc68503b..f5d9fc70a04c 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -375,6 +375,7 @@ static int __walk_iomem_res_desc(struct resource *res, unsigned long desc,
> int (*func)(struct resource *, void *))
> {
> u64 orig_end = res->end;
> + u64 orig_flags = res->flags;
> int ret = -1;
>
> while ((res->start < res->end) &&
> @@ -385,6 +386,7 @@ static int __walk_iomem_res_desc(struct resource *res, unsigned long desc,
>
> res->start = res->end + 1;
> res->end = orig_end;
> + res->flags = orig_flags;
> }
>
> return ret;
>

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