Re: [PATCH v2] cifs: fix regression when mounting shares with prefix paths

[Steve French <smfrench@gmail.com>]

added acked-by and merged into cifs-2.6.git for-next

On Mon, May 3, 2021 at 6:20 PM David Disseldorp <ddiss@suse.de> wrote:
>
> On Mon,  3 May 2021 11:55:26 -0300, Paulo Alcantara wrote:
>
> > The commit 315db9a05b7a ("cifs: fix leak in cifs_smb3_do_mount() ctx")
> > revealed an existing bug when mounting shares that contain a prefix
> > path or DFS links.
> >
> > cifs_setup_volume_info() requires the @devname to contain the full
> > path (UNC + prefix) to update the fs context with the new UNC and
> > prepath values, however we were passing only the UNC
> > path (old_ctx->UNC) in @device thus discarding any prefix paths.
> >
> > Instead of concatenating both old_ctx->{UNC,prepath} and pass it in
> > @devname, just keep the dup'ed values of UNC and prepath in
> > cifs_sb->ctx after calling smb3_fs_context_dup(), and fix
> > smb3_parse_devname() to correctly parse and not leak the new UNC and
> > prefix paths.
> >
> > Cc: <stable@vger.kernel.org> # v5.11+
> > Fixes: 315db9a05b7a ("cifs: fix leak in cifs_smb3_do_mount() ctx")
> > Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
> > ---
> >  fs/cifs/cifsfs.c     |  8 +-------
> >  fs/cifs/connect.c    | 24 ++++++++++++++++++------
> >  fs/cifs/fs_context.c |  4 ++++
> >  3 files changed, 23 insertions(+), 13 deletions(-)
> >
> > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> > index 8a6894577697..d7ea9c5fe0f8 100644
> > --- a/fs/cifs/cifsfs.c
> > +++ b/fs/cifs/cifsfs.c
> > @@ -863,13 +863,7 @@ cifs_smb3_do_mount(struct file_system_type *fs_type,
> >               goto out;
> >       }
> >
> > -     /* cifs_setup_volume_info->smb3_parse_devname() redups UNC & prepath */
> > -     kfree(cifs_sb->ctx->UNC);
> > -     cifs_sb->ctx->UNC = NULL;
> > -     kfree(cifs_sb->ctx->prepath);
> > -     cifs_sb->ctx->prepath = NULL;
> > -
> > -     rc = cifs_setup_volume_info(cifs_sb->ctx, NULL, old_ctx->UNC);
> > +     rc = cifs_setup_volume_info(cifs_sb->ctx, NULL, NULL);
>
> IIUC, with the new behaviour, this call becomes pretty much an
>         if (!cifs_sb->ctx->username)
>                 root = ERR_PTR(-EINVAL);
>
> So it might be worth simplifying this further. Either way:
> Acked-by: David Disseldorp <ddiss@suse.de>
>
> Cheers, David



-- 
Thanks,

Steve