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

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Message-ID: <aQov2KFhe8Ro3CtC@chcpu18>
Date: Tue, 4 Nov 2025 16:54:48 +0000
From: Shuhao Fu <sfual@....ust.hk>
To: Steve French <smfrench@...il.com>
Cc: Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.org>,
        Ronnie Sahlberg <ronniesahlberg@...il.com>,
        Shyam Prasad N <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
        Bharath SM <bharathsm@...rosoft.com>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] smb: client: fix refcount leak in smb2_set_path_attr

On Tue, Nov 04, 2025 at 10:12:13AM -0600, Steve French wrote:
> There are multiple callers - are there callers that don't call
> "set_writeable_path()" ?    And so could cause the reverse refcount
> issue?

I found three calls to `smb2_set_path_attr`. Two in `smb2_rename_path`
and one in `smb2_create_hardlink`. The one in `smb2_create_hardlink`
passes NULL for cfile. Therefore, it would not cause reverse refcount
issue here.

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)
> >
> >
> 
> 
> -- 
> Thanks,
> 
> Steve