2010-06-04 21:10:31

by Adam Lackorzynski

Subject: [PATCH] early_res: fix check in free_early_partial

free_early_partial must check the returned region of find_overlapped_early()
whether it is a region at all. Otherwise the function will indefinitely
loop.

Signed-off-by: Adam Lackorzynski <[email protected]>
---
kernel/early_res.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/early_res.c b/kernel/early_res.c
index 31aa933..9afcb4c 100644
--- a/kernel/early_res.c
+++ b/kernel/early_res.c
@@ -341,10 +341,11 @@ void __init free_early_partial(u64 start, u64 end)

try_next:
i = find_overlapped_early(start, end);
- if (i >= max_early_res)
+ r = &early_res[i];
+
+ if (i >= max_early_res || !r->end)
return;

- r = &early_res[i];
/* hole ? */
if (r->end >= end && r->start <= start) {
drop_range_partial(i, start, end);
--
1.7.1

2010-06-05 00:00:07

by Yinghai Lu

Subject: Re: [PATCH] early_res: fix check in free_early_partial

On Fri, Jun 4, 2010 at 2:10 PM, Adam Lackorzynski
<[email protected]> wrote:
> free_early_partial must check the returned region of find_overlapped_early()
> whether it is a region at all. Otherwise the function will indefinitely
> loop.

do you have that hang really?

that stage we should not have blank slot in the middle.

Thanks

Yinghai Lu

>
> Signed-off-by: Adam Lackorzynski <[email protected]>
> ---
> ?kernel/early_res.c | ? ?5 +++--
> ?1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/early_res.c b/kernel/early_res.c
> index 31aa933..9afcb4c 100644
> --- a/kernel/early_res.c
> +++ b/kernel/early_res.c
> @@ -341,10 +341,11 @@ void __init free_early_partial(u64 start, u64 end)
>
> ?try_next:
> ? ? ? ?i = find_overlapped_early(start, end);
> - ? ? ? if (i >= max_early_res)
> + ? ? ? r = &early_res[i];
> +
> + ? ? ? if (i >= max_early_res || !r->end)
> ? ? ? ? ? ? ? ?return;
>
> - ? ? ? r = &early_res[i];
> ? ? ? ?/* hole ? */
> ? ? ? ?if (r->end >= end && r->start <= start) {
> ? ? ? ? ? ? ? ?drop_range_partial(i, start, end);
> --
> 1.7.1
> --
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2010-06-06 11:32:55

by Adam Lackorzynski

Subject: Re: [PATCH] early_res: fix check in free_early_partial

On Fri Jun 04, 2010 at 17:00:02 -0700, Yinghai Lu wrote:
> On Fri, Jun 4, 2010 at 2:10 PM, Adam Lackorzynski
> <[email protected]> wrote:
> > free_early_partial must check the returned region of find_overlapped_early()
> > whether it is a region at all. Otherwise the function will indefinitely
> > loop.
>
> do you have that hang really?
>
> that stage we should not have blank slot in the middle.

I did but I cannot manage to reproduce this now. I think this happens
when find_overlapped_early does not find a region, i.e. the given one
does not exist. Then it returns i == early_res_count which is smaller
than max_early_res (usually). Given that r->end == 0 this goes on
indefinitely. So the check would just be more robust with
i >= max_early_res || !r->end or i == early_res_count.

Adam

> > Signed-off-by: Adam Lackorzynski <[email protected]>
> > ---
> > ?kernel/early_res.c | ? ?5 +++--
> > ?1 files changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/early_res.c b/kernel/early_res.c
> > index 31aa933..9afcb4c 100644
> > --- a/kernel/early_res.c
> > +++ b/kernel/early_res.c
> > @@ -341,10 +341,11 @@ void __init free_early_partial(u64 start, u64 end)
> >
> > ?try_next:
> > ? ? ? ?i = find_overlapped_early(start, end);
> > - ? ? ? if (i >= max_early_res)
> > + ? ? ? r = &early_res[i];
> > +
> > + ? ? ? if (i >= max_early_res || !r->end)
> > ? ? ? ? ? ? ? ?return;
> >
> > - ? ? ? r = &early_res[i];
> > ? ? ? ?/* hole ? */
> > ? ? ? ?if (r->end >= end && r->start <= start) {
> > ? ? ? ? ? ? ? ?drop_range_partial(i, start, end);
> > --
> > 1.7.1
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to [email protected]
> > More majordomo info at ?http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at ?http://www.tux.org/lkml/
> >