> On Nov 19, 2020, at 9:30 AM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote:
>
> On Thu, 2020-11-19 at 09:17 -0500, Chuck Lever wrote:
>>
>>
>>> On Nov 18, 2020, at 5:19 PM, trondmy@xxxxxxxxxx wrote:
>>>
>>> From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>>>
>>> When doing a read() into a page, we also don't care if the nul
>>> padding
>>> stays in that last page when the data length is not 32-bit aligned.
>>
>> What if the READ payload lands in the middle of a file? The
>> pad on the end will overwrite file content just past where
>> the READ payload lands.
>
> If the size > buf->page_len, then it gets truncated in
> xdr_align_pages() afaik.
I will need to check how RPC/RDMA behaves. It might build a
chunk that includes the pad in this case, which would break
things.
>>> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>>> ---
>>> fs/nfs/nfs2xdr.c | 2 +-
>>> fs/nfs/nfs3xdr.c | 2 +-
>>> fs/nfs/nfs4xdr.c | 2 +-
>>> 3 files changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
>>> index db9c265ad9e1..468bfbfe44d7 100644
>>> --- a/fs/nfs/nfs2xdr.c
>>> +++ b/fs/nfs/nfs2xdr.c
>>> @@ -102,7 +102,7 @@ static int decode_nfsdata(struct xdr_stream
>>> *xdr, struct nfs_pgio_res *result)
>>> if (unlikely(!p))
>>> return -EIO;
>>> count = be32_to_cpup(p);
>>> - recvd = xdr_read_pages(xdr, count);
>>> + recvd = xdr_read_pages(xdr, xdr_align_size(count));
>>> if (unlikely(count > recvd))
>>> goto out_cheating;
>>> out:
>>> diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
>>> index d3e1726d538b..8ef7c961d3e2 100644
>>> --- a/fs/nfs/nfs3xdr.c
>>> +++ b/fs/nfs/nfs3xdr.c
>>> @@ -1611,7 +1611,7 @@ static int decode_read3resok(struct
>>> xdr_stream *xdr,
>>> ocount = be32_to_cpup(p++);
>>> if (unlikely(ocount != count))
>>> goto out_mismatch;
>>> - recvd = xdr_read_pages(xdr, count);
>>> + recvd = xdr_read_pages(xdr, xdr_align_size(count));
>>> if (unlikely(count > recvd))
>>> goto out_cheating;
>>> out:
>>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>>> index 755b556e85c3..5baa767106dc 100644
>>> --- a/fs/nfs/nfs4xdr.c
>>> +++ b/fs/nfs/nfs4xdr.c
>>> @@ -5202,7 +5202,7 @@ static int decode_read(struct xdr_stream
>>> *xdr, struct rpc_rqst *req,
>>> return -EIO;
>>> eof = be32_to_cpup(p++);
>>> count = be32_to_cpup(p);
>>> - recvd = xdr_read_pages(xdr, count);
>>> + recvd = xdr_read_pages(xdr, xdr_align_size(count));
>>> if (count > recvd) {
>>> dprintk("NFS: server cheating in read reply: "
>>> "count %u > recvd %u\n", count,
>>> recvd);
>>> --
>>> 2.28.0
>>>
>>
>> --
>> Chuck Lever
>>
>>
>>
>
> --
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@xxxxxxxxxxxxxxx
--
Chuck Lever
