[Ocfs2-devel] [patch 04/15] ocfs2: avoid access invalid address when read o2dlm debug messages
jiangyiwen
jiangyiwen at huawei.com
Fri Dec 19 00:34:39 PST 2014
在 2014/12/17 6:26, Mark Fasheh 写道:
> On Mon, Dec 15, 2014 at 02:51:00PM -0800, Andrew Morton wrote:
>> In such a race case, invalid address access may occurs. So we should
>> delete list res->tracking before resA->refs decrease to 0.
>>
>
>
>> diff -puN fs/ocfs2/dlm/dlmmaster.c~ocfs2-avoid-access-invalid-address-when-read-o2dlm-debug-messages fs/ocfs2/dlm/dlmmaster.c
>> --- a/fs/ocfs2/dlm/dlmmaster.c~ocfs2-avoid-access-invalid-address-when-read-o2dlm-debug-messages
>> +++ a/fs/ocfs2/dlm/dlmmaster.c
>> @@ -498,16 +498,6 @@ static void dlm_lockres_release(struct k
>> mlog(0, "destroying lockres %.*s\n", res->lockname.len,
>> res->lockname.name);
>>
>> - spin_lock(&dlm->track_lock);
>> - if (!list_empty(&res->tracking))
>> - list_del_init(&res->tracking);
>> - else {
>> - mlog(ML_ERROR, "Resource %.*s not on the Tracking list\n",
>> - res->lockname.len, res->lockname.name);
>> - dlm_print_one_lock_resource(res);
>> - }
>> - spin_unlock(&dlm->track_lock);
>> -
>> atomic_dec(&dlm->res_cur_count);
>>
>> if (!hlist_unhashed(&res->hash_node) ||
>> diff -puN fs/ocfs2/dlm/dlmthread.c~ocfs2-avoid-access-invalid-address-when-read-o2dlm-debug-messages fs/ocfs2/dlm/dlmthread.c
>> --- a/fs/ocfs2/dlm/dlmthread.c~ocfs2-avoid-access-invalid-address-when-read-o2dlm-debug-messages
>> +++ a/fs/ocfs2/dlm/dlmthread.c
>> @@ -211,6 +211,16 @@ static void dlm_purge_lockres(struct dlm
>>
>> __dlm_unhash_lockres(dlm, res);
>>
>> + spin_lock(&dlm->track_lock);
>> + if (!list_empty(&res->tracking))
>> + list_del_init(&res->tracking);
>> + else {
>> + mlog(ML_ERROR, "Resource %.*s not on the Tracking list\n",
>> + res->lockname.len, res->lockname.name);
>> + __dlm_print_one_lock_resource(res);
>> + }
>> + spin_unlock(&dlm->track_lock);
>> +
>> /* lockres is not in the hash now. drop the flag and wake up
>> * any processes waiting in dlm_get_lock_resource. */
>> if (!master) {
>> _
>
> How do we know that dlm_purge_lockres() is the last caller of
> dlm_lockres_put()? Don't we now have a problem where if the last ref is
> dropped by any other function than dlm_purge_lockres() the lockres is freed
> while on the tracking list?
> --Mark
>
> --
> Mark Fasheh
>
> .
>
dlm_purge_lockres is not necessarily the last caller of
dlm_lockres_put(), but it means lockres will be purged if
dlm_purge_lockres is called. Besides, lockres is also unhashed in
dlm_purge_lockres, so lockres can be removed from tracking list.
contents of dlm->tracking_list will be consistent with
dlm->lockres_hash.
--YiWen Jiang
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