linux-kernel - Re: [PATCH] smb: client: fix refcount leak in smb2_set_path

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Message-ID: <33de0eaf-474b-4e88-a445-2f12387bc36c@suse.com>
Date: Tue, 4 Nov 2025 15:34:12 -0300
From: Henrique Carvalho <henrique.carvalho@...e.com>
To: Shuhao Fu <sfual@....ust.hk>
Cc: Steve French <smfrench@...il.com>, Tom Talpey <tom@...pey.com>,
 Shyam Prasad N <sprasad@...rosoft.com>, Paulo Alcantara <pc@...guebit.org>,
 linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
 linux-kernel@...r.kernel.org, Steve French <sfrench@...ba.org>,
 Bharath SM <bharathsm@...rosoft.com>
Subject: Re: [PATCH] smb: client: fix refcount leak in smb2_set_path_attr



On 11/4/25 1:56 PM, Shuhao Fu wrote:
> On Tue, Nov 04, 2025 at 01:23:33PM -0300, Henrique Carvalho wrote:
>>
>>
>> On 11/4/25 1:12 PM, Steve French via samba-technical wrote:
>>> There are multiple callers - are there callers that don't call
>>> "set_writeable_path()" ?    And so could cause the reverse refcount
>>> issue?
>>
>> Yes... Even if it does not cause an issue today, that fix looks like it
>> belongs inside smb2_rename_path?
> 
> I placed decrement in `smb2_set_path_attr` since it seems like a wrapper
> of `smb2_compound_op`. I figured that this wrapper should handle the
> failure cases the same way as `smb2_compound_op`.

Makes sense.

Acked-by: Henrique Carvalho <henrique.carvalho@...e.com>

> 
> Thanks,
> Shuhao
>>
>>>
>>> On Tue, Nov 4, 2025 at 9:21 AM Shuhao Fu <sfual@....ust.hk> wrote:
>>>>
>>>> Fix refcount leak in `smb2_set_path_attr` when path conversion fails.
>>>>
>>>> Function `cifs_get_writable_path` returns `cfile` with its reference
>>>> counter `cfile->count` increased on success. Function `smb2_compound_op`
>>>> would decrease the reference counter for `cfile`, as stated in its
>>>> comment. By calling `smb2_rename_path`, the reference counter of `cfile`
>>>> would leak if `cifs_convert_path_to_utf16` fails in `smb2_set_path_attr`.
>>>>
>>>> Fixes: 8de9e86c67ba ("cifs: create a helper to find a writeable handle by path name")
>>>> Signed-off-by: Shuhao Fu <sfual@....ust.hk>
>>>> ---
>>>>  fs/smb/client/smb2inode.c | 2 ++
>>>>  1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
>>>> index 09e3fc81d..69cb81fa0 100644
>>>> --- a/fs/smb/client/smb2inode.c
>>>> +++ b/fs/smb/client/smb2inode.c
>>>> @@ -1294,6 +1294,8 @@ static int smb2_set_path_attr(const unsigned int xid, struct cifs_tcon *tcon,
>>>>         smb2_to_name = cifs_convert_path_to_utf16(to_name, cifs_sb);
>>>>         if (smb2_to_name == NULL) {
>>>>                 rc = -ENOMEM;
>>>> +               if (cfile)
>>>> +                       cifsFileInfo_put(cfile);
>>>>                 goto smb2_rename_path;
>>>>         }
>>>>         in_iov.iov_base = smb2_to_name;
>>>> --
>>>> 2.39.5 (Apple Git-154)
>>>>
>>>>
>>>
>>>
>>
>> -- 
>> Henrique
>> SUSE Labs

-- 
Henrique
SUSE Labs