Re: [PATCH -next v2] cifsd: check return value of ksmbd_vfs_getcasexattr() correctly

[Yang Yingliang]

On 2021/5/31 13:38, Hyunchul Lee wrote:
> 2021년 5월 31일 (월) 오후 12:01, Yang Yingliang <yangyingliang@xxxxxxxxxx>님이 작성:
> > If ksmbd_vfs_getcasexattr() returns -ENOMEM, stream_buf is NULL,
> > it will cause null-ptr-deref when using it to copy memory. So we
> > need check the return value of ksmbd_vfs_getcasexattr() by comparing
> > with 0.
> >
> > Fixes: f44158485826 ("cifsd: add file operations")
> > Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
> > ---
> > v2:
> >    Handle the case ksmbd_vfs_getcasexattr() returns 0.
> > ---
> >   fs/cifsd/vfs.c | 10 ++++------
> >   1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/fs/cifsd/vfs.c b/fs/cifsd/vfs.c
> > index 97d5584ec870..2a9cc0bc7726 100644
> > --- a/fs/cifsd/vfs.c
> > +++ b/fs/cifsd/vfs.c
> > @@ -274,7 +274,6 @@ static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
> >   {
> >          ssize_t v_len;
> >          char *stream_buf = NULL;
> > -       int err;
> >
> >          ksmbd_debug(VFS, "read stream data pos : %llu, count : %zd\n",
> >                      *pos, count);
> > @@ -283,10 +282,9 @@ static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
> >                                         fp->stream.name,
> >                                         fp->stream.size,
> >                                         &stream_buf);
> > -       if (v_len == -ENOENT) {
> > +       if ((int)v_len <= 0) {
> >                  ksmbd_err("not found stream in xattr : %zd\n", v_len);
> > -               err = -ENOENT;
> > -               return err;
> > +               return v_len == 0 ? -ENOENT : (int)v_len;
> How about making ksmbd_vfs_getcasexattr return -ENONENT instead of
> returning 0 to
> remove duplicate error handling code?
Yes, I think it's ok, I will send a v3 later.

Thanks,
Yang
> Thanks,
> Hyunchul
>
> >          }
> >
> >          memcpy(buf, &stream_buf[*pos], count);
> > @@ -415,9 +413,9 @@ static int ksmbd_vfs_stream_write(struct ksmbd_file *fp, char *buf, loff_t *pos,
> >                                         fp->stream.name,
> >                                         fp->stream.size,
> >                                         &stream_buf);
> > -       if (v_len == -ENOENT) {
> > +       if ((int)v_len <= 0) {
> >                  ksmbd_err("not found stream in xattr : %zd\n", v_len);
> > -               err = -ENOENT;
> > +               err = v_len == 0 ? -ENOENT : (int)v_len;
> >                  goto out;
> >          }
> >
> > --
> > 2.25.1
> .