* [PATCH v3] kernel/resource.c: fix stack overflow in __reserve_region_with_split
@ 2012-09-07 22:08 T Makphaibulchoke
2012-09-10 4:44 ` Ram Pai
0 siblings, 1 reply; 2+ messages in thread
From: T Makphaibulchoke @ 2012-09-07 22:08 UTC (permalink / raw)
To: akpm, linuxram, paul.gortmaker, weiyang, linux-kernel; +Cc: T Makphaibulchoke
Using recurvise call to try adding a non-conflicting region in the function
__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>
---
Change since v2:
* Initializing both the name and flags fileds of the newly allocated region
request.
Change since v1:
* Fixing __resrve_region_with_split() to ensure a reqion reserve request is
satisfied to the fullest extent, minus any overlapping conflicting regions.
---
kernel/resource.c | 50 ++++++++++++++++++++++++++++++++++++++------------
1 files changed, 38 insertions(+), 12 deletions(-)
diff --git a/kernel/resource.c b/kernel/resource.c
index 34d4588..73f35d4 100644
--- a/kernel/resource.c
+++ b/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,
--
1.7.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3] kernel/resource.c: fix stack overflow in __reserve_region_with_split
2012-09-07 22:08 [PATCH v3] kernel/resource.c: fix stack overflow in __reserve_region_with_split T Makphaibulchoke
@ 2012-09-10 4:44 ` Ram Pai
0 siblings, 0 replies; 2+ messages in thread
From: Ram Pai @ 2012-09-10 4:44 UTC (permalink / raw)
To: T Makphaibulchoke; +Cc: akpm, linuxram, paul.gortmaker, weiyang, linux-kernel
On Fri, Sep 07, 2012 at 04:08:19PM -0600, T Makphaibulchoke wrote:
> Using recurvise call to try adding a non-conflicting region in the function
> __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>
>
> ---
> Change since v2:
> * Initializing both the name and flags fileds of the newly allocated region
> request.
>
> Change since v1:
> * Fixing __resrve_region_with_split() to ensure a reqion reserve request is
> satisfied to the fullest extent, minus any overlapping conflicting regions.
> ---
> kernel/resource.c | 50 ++++++++++++++++++++++++++++++++++++++------------
> 1 files changed, 38 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 34d4588..73f35d4 100644
> --- a/kernel/resource.c
> +++ b/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,
Reviewed-by: Ram Pai <linuxram@us.ibm.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
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