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

From: Thorsten Blum
Date: Tue Aug 20 2024 - 12:33:49 EST


On 20. Aug 2024, at 16:52, Tom Talpey <tom@xxxxxxxxxx> wrote:
> 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.

Just to clarify before I submit a v2: Is a strict "<" and without "+1"
correct?

>>> 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.

Same here, strict "<" and without "+ 1"? Or just a refactor to "<="
without changing the condition?

Thanks,
Thorsten