Re: [PATCH] ksmbd: Replace one-element arrays with flexible-array members

[Tom Talpey]

On 8/20/2024 10:11 AM, Namjae Jeon wrote:
> On Mon, Aug 19, 2024 at 1:22 AM Thorsten Blum <thorsten.blum@xxxxxxxxxx> wrote:
> > Replace the deprecated one-element arrays with flexible-array members
> > in the structs copychunk_ioctl_req and smb2_ea_info_req.
> >
> > There are no binary differences after this conversion.
> >
> > Link: https://github.com/KSPP/linux/issues/79
> > Signed-off-by: Thorsten Blum <thorsten.blum@xxxxxxxxxx>
> > ---
> >   fs/smb/server/smb2pdu.c | 4 ++--
> >   fs/smb/server/smb2pdu.h | 4 ++--
> >   2 files changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
> > index 2df1354288e6..83667cb78fa6 100644
> > --- a/fs/smb/server/smb2pdu.c
> > +++ b/fs/smb/server/smb2pdu.c
> > @@ -4580,7 +4580,7 @@ static int smb2_get_ea(struct ksmbd_work *work, struct ksmbd_file *fp,
> >          /* single EA entry is requested with given user.* name */
> >          if (req->InputBufferLength) {
> >                  if (le32_to_cpu(req->InputBufferLength) <
> > -                   sizeof(struct smb2_ea_info_req))
> > +                   sizeof(struct smb2_ea_info_req) + 1)
> We can use <= instead of +1.

This is better, but maybe this test was actually not right in
the first place.

I think a strict "<" is correct here, because the ea name
field is a counted array of length EaNameLength. So, it's
a layering issue to fail with EINVAL this early in the
processing. All that should be checked up front is
that a complete smb2_ea_info_req header is present.

> >                          return -EINVAL;
> >
> >                  ea_req = (struct smb2_ea_info_req *)((char *)req +
> > @@ -8083,7 +8083,7 @@ int smb2_ioctl(struct ksmbd_work *work)
> >                          goto out;
> >                  }
> >
> > -               if (in_buf_len < sizeof(struct copychunk_ioctl_req)) {
> > +               if (in_buf_len < sizeof(struct copychunk_ioctl_req) + 1) {
> Ditto.

And ditto.

Tom.

> >                          ret = -EINVAL;
> >                          goto out;
> >                  }
> > diff --git a/fs/smb/server/smb2pdu.h b/fs/smb/server/smb2pdu.h
> > index 3be7d5ae65a8..73aff20e22d0 100644
> > --- a/fs/smb/server/smb2pdu.h
> > +++ b/fs/smb/server/smb2pdu.h
> > @@ -194,7 +194,7 @@ struct copychunk_ioctl_req {
> >          __le64 ResumeKey[3];
> >          __le32 ChunkCount;
> >          __le32 Reserved;
> > -       __u8 Chunks[1]; /* array of srv_copychunk */
> > +       __u8 Chunks[]; /* array of srv_copychunk */
> >   } __packed;
> >
> >   struct srv_copychunk {
> > @@ -370,7 +370,7 @@ struct smb2_file_attr_tag_info {
> >   struct smb2_ea_info_req {
> >          __le32 NextEntryOffset;
> >          __u8   EaNameLength;
> > -       char name[1];
> > +       char name[];
> >   } __packed; /* level 15 Query */
> >
> >   struct smb2_ea_info {
> > --
> > 2.46.0