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kernel/resource.c: fix stack overflow in __reserve_region_with_split()

Using a recursive call add a non-conflicting region in
__reserve_region_with_split() could result in a stack overflow in the case
that the recursive calls are too deep.  Convert the recursive calls to an
iterative loop to avoid the problem.

Tested on a machine containing 135 regions.  The kernel no longer panicked
with stack overflow.

Also tested with code arbitrarily adding regions with no conflict,
embedding two consecutive conflicts and embedding two non-consecutive
conflicts.

Signed-off-by: T Makphaibulchoke <tmac@hp.com>
Reviewed-by: Ram Pai <linuxram@us.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@gmail.com>
Cc: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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commit 4965f5667f36a95b41cda6638875bc992bd7d18b 1 parent c99b684
T Makphaibulchoke authored committed
Showing with 38 additions and 12 deletions.
  1. +38 −12 kernel/resource.c
View
50 kernel/resource.c
@@ -763,6 +763,7 @@ static void __init __reserve_region_with_split(struct resource *root,
struct resource *parent = root;
struct resource *conflict;
struct resource *res = kzalloc(sizeof(*res), GFP_ATOMIC);
+ struct resource *next_res = NULL;
if (!res)
return;
@@ -772,21 +773,46 @@ static void __init __reserve_region_with_split(struct resource *root,
res->end = end;
res->flags = IORESOURCE_BUSY;
- conflict = __request_resource(parent, res);
- if (!conflict)
- return;
+ while (1) {
- /* failed, split and try again */
- kfree(res);
+ conflict = __request_resource(parent, res);
+ if (!conflict) {
+ if (!next_res)
+ break;
+ res = next_res;
+ next_res = NULL;
+ continue;
+ }
- /* conflict covered whole area */
- if (conflict->start <= start && conflict->end >= end)
- return;
+ /* conflict covered whole area */
+ if (conflict->start <= res->start &&
+ conflict->end >= res->end) {
+ kfree(res);
+ WARN_ON(next_res);
+ break;
+ }
+
+ /* failed, split and try again */
+ if (conflict->start > res->start) {
+ end = res->end;
+ res->end = conflict->start - 1;
+ if (conflict->end < end) {
+ next_res = kzalloc(sizeof(*next_res),
+ GFP_ATOMIC);
+ if (!next_res) {
+ kfree(res);
+ break;
+ }
+ next_res->name = name;
+ next_res->start = conflict->end + 1;
+ next_res->end = end;
+ next_res->flags = IORESOURCE_BUSY;
+ }
+ } else {
+ res->start = conflict->end + 1;
+ }
+ }
- if (conflict->start > start)
- __reserve_region_with_split(root, start, conflict->start-1, name);
- if (conflict->end < end)
- __reserve_region_with_split(root, conflict->end+1, end, name);
}
void __init reserve_region_with_split(struct resource *root,
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