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

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Message-ID: <aQowQ7gCdDruGVro@chcpu18>
Date: Tue, 4 Nov 2025 16:56:35 +0000
From: Shuhao Fu <sfual@....ust.hk>
To: Henrique Carvalho <henrique.carvalho@...e.com>
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 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`.

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