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Subject[PATCH 1/3 v2] resource: fix an error which walks through iomem resources
Date
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: Dave Young <dyoung@redhat.com>
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;
--
2.17.1
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