[Ocfs2-devel] [PATCH 1/1] Ocfs2: Handle invalid lock_res in lockres_seq_start() for dlmdebug.c
tristan
tristan.ye at oracle.com
Thu Sep 9 18:20:50 PDT 2010
Sunil Mushran wrote:
> On 09/09/2010 02:16 AM, Tristan Ye wrote:
>> In lockres_seq_start() of dlmdebug.c, when you looking at following
>> piece of codes:
>>
>> list_for_each_entry(res, track_list, tracking) {
>> if (&res->tracking ==&dlm->tracking_list)
>> res = NULL;
>> else
>> dlm_lockres_get(res);
>> break;
>> }
>>
>> ...
>>
>> if (res) {
>> spin_lock(&res->spinlock);
>> dump_lockres(res, dl->dl_buf, dl->dl_len - 1);
>> spin_unlock(&res->spinlock);
>> } else
>> dl = NULL;
>>
>> One thought can come to you that, in the case of 'an-empty-list',
>> cursor 'res'
>> here is not an INVALID pointer for real dlm_lock_resource object, it
>> is nothing
>> than a fake address figured out by arbitary 'container_of()' way, the
>> patch tries
>> to check track_list, and avoid accessing an invalid pointer if the
>> list is empty,
>> it fixes following oops:
>>
>> http://oss.oracle.com/bugzilla/show_bug.cgi?id=1287
>>
>> Signed-off-by: Tristan Ye<tristan.ye at oracle.com>
>> ---
>>
>
> Such a detailed description is only required if the bug fix
> is complicated. This is a simple fix. Just say that this handles
> the case in which the dlm->tracking_list is empty and mention
> the bz.
>
Yeah, kind of...
>> fs/ocfs2/dlm/dlmdebug.c | 7 +++++++
>> 1 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/fs/ocfs2/dlm/dlmdebug.c b/fs/ocfs2/dlm/dlmdebug.c
>> index 5efdd37..06d668a 100644
>> --- a/fs/ocfs2/dlm/dlmdebug.c
>> +++ b/fs/ocfs2/dlm/dlmdebug.c
>> @@ -639,6 +639,12 @@ static void *lockres_seq_start(struct seq_file
>> *m, loff_t *pos)
>> else
>> track_list =&dlm->tracking_list;
>>
>> + if (list_empty(track_list)) {
>> + dl = NULL;
>> + spin_unlock(&dlm->track_lock);
>> + goto bail;
>> + }
>> +
>>
>
> You should add this check as part of the else block above so
> that we check for empty list only at the start.
So we just don't need to check list 'oldres->tracking'?
>
>> list_for_each_entry(res, track_list, tracking) {
>> if (&res->tracking ==&dlm->tracking_list)
>> res = NULL;
>> @@ -660,6 +666,7 @@ static void *lockres_seq_start(struct seq_file
>> *m, loff_t *pos)
>> } else
>> dl = NULL;
>>
>> +bail:
>> /* passed to seq_show */
>> return dl;
>> }
>>
>
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