Re: [RFC PATCH] nfs: use nfsi->rwsem to protect traversal of the file lock list

Gently ping...

This patch has been reviewed, but leave alone here for a long time...

在 2026/5/8 16:33, yangerkun 写道:
> Gently ping...
> 
> 在 2026/4/16 11:01, yangerkun 写道:
>> Hi Anna and Trond,
>>
>> Could you please help check if there are any issues with this patch, and
>> if there are none, could you help merge it in?
>>
>> Thanks,
>> Erkun.
>>
>> 在 2026/3/9 22:09, Jeff Layton 写道:
>>> On Thu, 2026-02-26 at 09:22 +0800, Yang Erkun wrote:
>>>> Lingfeng identified a bug and suggested two solutions, but both appear
>>>> to have issues.
>>>>
>>>> Generally, we cannot release flc_lock while iterating over the file 
>>>> lock
>>>> list to avoid use-after-free (UAF) problems with file locks. However,
>>>> functions like nfs_delegation_claim_locks and nfs4_reclaim_locks cannot
>>>> adhere to this rule because recover_lock or nfs4_lock_delegation_recall
>>>> may take a long time. To resolve this, NFS switches to using nfsi- 
>>>> >rwsem
>>>> for the same protection, and nfs_reclaim_locks follows this approach.
>>>> Although nfs_delegation_claim_locks uses so_delegreturn_mutex instead,
>>>> this is inadequate since a single inode can have multiple nfs4_state
>>>> instances. Therefore, the fix is to also use nfsi->rwsem in this case.
>>>>
>>>> Furthermore, after commit c69899a17ca4 ("NFSv4: Update of VFS byte 
>>>> range
>>>> lock must be atomic with the stateid update"), the functions
>>>> nfs4_locku_done and nfs4_lock_done also break this rule because they
>>>> call locks_lock_inode_wait without holding nfsi->rwsem. Simply adding
>>>> this protection could cause many deadlocks, so instead, the call to
>>>> locks_lock_inode_wait is moved into _nfs4_proc_setlk. Regarding the bug
>>>> fixed by commit c69899a17ca4 ("NFSv4: Update of VFS byte range
>>>> lock must be atomic with the stateid update"), it has been resolved
>>>> after commit 0460253913e5 ("NFSv4: nfs4_do_open() is incorrectly 
>>>> triggering
>>>> state recovery") because all slots are drained before calling
>>>> nfs4_do_reclaim, which prevents concurrent stateid changes along 
>>>> this path.
>>>> Also, nfs_delegation_claim_locks does not cause this concurrency either
>>>> since when _nfs4_proc_setlk is called with NFS_DELEGATED_STATE, no 
>>>> RPC is
>>>> sent, so nfs4_lock_done is not called. Therefore,
>>>> nfs4_lock_delegation_recall from nfs_delegation_claim_locks is the 
>>>> first
>>>> time the stateid is set.
>>>>
>>>> Reported-by: Li Lingfeng <[email protected]>
>>>> Closes: https://lore.kernel.org/all/20250419085709.1452492-1- 
>>>> [email protected]/
>>>> Closes: https://lore.kernel.org/all/20250715030559.2906634-1- 
>>>> [email protected]/
>>>> Fixes: c69899a17ca4 ("NFSv4: Update of VFS byte range lock must be 
>>>> atomic with the stateid update")
>>>> Signed-off-by: Yang Erkun <[email protected]>
>>>> ---
>>>>   fs/nfs/delegation.c     |  9 ++++++++-
>>>>   fs/nfs/nfs4proc.c       | 22 +++++++++++-----------
>>>>   include/linux/nfs_xdr.h |  1 -
>>>>   3 files changed, 19 insertions(+), 13 deletions(-)
>>>>
>>>> diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
>>>> index 122fb3f14ffb..9546d2195c25 100644
>>>> --- a/fs/nfs/delegation.c
>>>> +++ b/fs/nfs/delegation.c
>>>> @@ -173,6 +173,7 @@ int nfs4_check_delegation(struct inode *inode, 
>>>> fmode_t type)
>>>>   static int nfs_delegation_claim_locks(struct nfs4_state *state, 
>>>> const nfs4_stateid *stateid)
>>>>   {
>>>>       struct inode *inode = state->inode;
>>>> +    struct nfs_inode *nfsi = NFS_I(inode);
>>>>       struct file_lock *fl;
>>>>       struct file_lock_context *flctx = locks_inode_context(inode);
>>>>       struct list_head *list;
>>>> @@ -182,6 +183,9 @@ static int nfs_delegation_claim_locks(struct 
>>>> nfs4_state *state, const nfs4_state
>>>>           goto out;
>>>>       list = &flctx->flc_posix;
>>>> +
>>>> +    /* Guard against reclaim and new lock/unlock calls */
>>>> +    down_write(&nfsi->rwsem);
>>>>       spin_lock(&flctx->flc_lock);
>>>>   restart:
>>>>       for_each_file_lock(fl, list) {
>>>> @@ -189,8 +193,10 @@ static int nfs_delegation_claim_locks(struct 
>>>> nfs4_state *state, const nfs4_state
>>>>               continue;
>>>>           spin_unlock(&flctx->flc_lock);
>>>>           status = nfs4_lock_delegation_recall(fl, state, stateid);
>>>> -        if (status < 0)
>>>> +        if (status < 0) {
>>>> +            up_write(&nfsi->rwsem);
>>>>               goto out;
>>>> +        }
>>>>           spin_lock(&flctx->flc_lock);
>>>>       }
>>>>       if (list == &flctx->flc_posix) {
>>>> @@ -198,6 +204,7 @@ static int nfs_delegation_claim_locks(struct 
>>>> nfs4_state *state, const nfs4_state
>>>>           goto restart;
>>>>       }
>>>>       spin_unlock(&flctx->flc_lock);
>>>> +    up_write(&nfsi->rwsem);
>>>>   out:
>>>>       return status;
>>>>   }
>>>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>>>> index 91bcf67bd743..9d6fbca8798b 100644
>>>> --- a/fs/nfs/nfs4proc.c
>>>> +++ b/fs/nfs/nfs4proc.c
>>>> @@ -7076,7 +7076,6 @@ static void nfs4_locku_done(struct rpc_task 
>>>> *task, void *data)
>>>>       switch (task->tk_status) {
>>>>           case 0:
>>>>               renew_lease(calldata->server, calldata->timestamp);
>>>> -            locks_lock_inode_wait(calldata->lsp->ls_state->inode, 
>>>> &calldata->fl);
>>>>               if (nfs4_update_lock_stateid(calldata->lsp,
>>>>                       &calldata->res.stateid))
>>>>                   break;
>>>> @@ -7344,11 +7343,6 @@ static void nfs4_lock_done(struct rpc_task 
>>>> *task, void *calldata)
>>>>       case 0:
>>>>           renew_lease(NFS_SERVER(d_inode(data->ctx->dentry)),
>>>>                   data->timestamp);
>>>> -        if (data->arg.new_lock && !data->cancelled) {
>>>> -            data->fl.c.flc_flags &= ~(FL_SLEEP | FL_ACCESS);
>>>> -            if (locks_lock_inode_wait(lsp->ls_state->inode, &data- 
>>>> >fl) < 0)
>>>> -                goto out_restart;
>>>> -        }
>>>>           if (data->arg.new_lock_owner != 0) {
>>>>               nfs_confirm_seqid(&lsp->ls_seqid, 0);
>>>>               nfs4_stateid_copy(&lsp->ls_stateid, &data->res.stateid);
>>>> @@ -7459,11 +7453,10 @@ static int _nfs4_do_setlk(struct nfs4_state 
>>>> *state, int cmd, struct file_lock *f
>>>>       msg.rpc_argp = &data->arg;
>>>>       msg.rpc_resp = &data->res;
>>>>       task_setup_data.callback_data = data;
>>>> -    if (recovery_type > NFS_LOCK_NEW) {
>>>> -        if (recovery_type == NFS_LOCK_RECLAIM)
>>>> -            data->arg.reclaim = NFS_LOCK_RECLAIM;
>>>> -    } else
>>>> -        data->arg.new_lock = 1;
>>>> +
>>>> +    if (recovery_type == NFS_LOCK_RECLAIM)
>>>> +        data->arg.reclaim = NFS_LOCK_RECLAIM;
>>>> +
>>>>       task = rpc_run_task(&task_setup_data);
>>>>       if (IS_ERR(task))
>>>>           return PTR_ERR(task);
>>>> @@ -7573,6 +7566,13 @@ static int _nfs4_proc_setlk(struct nfs4_state 
>>>> *state, int cmd, struct file_lock
>>>>       up_read(&nfsi->rwsem);
>>>>       mutex_unlock(&sp->so_delegreturn_mutex);
>>>>       status = _nfs4_do_setlk(state, cmd, request, NFS_LOCK_NEW);
>>>> +    if (status)
>>>> +        goto out;
>>>> +
>>>> +    down_read(&nfsi->rwsem);
>>>> +    request->c.flc_flags &= ~(FL_SLEEP | FL_ACCESS);
>>>> +    status = locks_lock_inode_wait(state->inode, request);
>>>> +    up_read(&nfsi->rwsem);
>>>>   out:
>>>>       request->c.flc_flags = flags;
>>>>       return status;
>>>> diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
>>>> index ff1f12aa73d2..9599ad15c3ad 100644
>>>> --- a/include/linux/nfs_xdr.h
>>>> +++ b/include/linux/nfs_xdr.h
>>>> @@ -580,7 +580,6 @@ struct nfs_lock_args {
>>>>       struct nfs_lowner    lock_owner;
>>>>       unsigned char        block : 1;
>>>>       unsigned char        reclaim : 1;
>>>> -    unsigned char        new_lock : 1;
>>>>       unsigned char        new_lock_owner : 1;
>>>>   };
>>>
>>> Nice work!
>>>
>>> Reviewed-by: Jeff Layton <[email protected]>
>>>
>>>
>>
> 
> 
>