Re: [RFC] problems with alloc_file_pseudo() use in __nfs42_ssc_open()

dai.ngo
2022-08-19T02:52:06Z

On 8/18/22 6:13 AM, Olga Kornievskaia wrote:
> On Thu, Aug 18, 2022 at 1:52 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
>> On Thu, Aug 18, 2022 at 08:19:54AM +0300, Amir Goldstein wrote:
>>
>>> NFS spec does not guarantee the safety of the server.
>>> It's like saying that the Law makes Crime impossible.
>>> The law needs to be enforced, so if server gets a request
>>> to COPY from/to an fhandle that resolves as a non-regular file
>>> (from a rogue or buggy NFS client) the server should return an
>>> error and not continue to alloc_file_pseudo().
>> FWIW, my preference would be to have alloc_file_pseudo() reject
>> directory inodes if it ever gets such.
>>
>> I'm still not sure that my (and yours, apparently) interpretation
>> of what Olga said is correct, though.
> Would it be appropriate to do the following then:
>
> diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
> index e88f6b18445e..112134b6438d 100644
> --- a/fs/nfs/nfs4file.c
> +++ b/fs/nfs/nfs4file.c
> @@ -340,6 +340,11 @@ static struct file *__nfs42_ssc_open(struct
> vfsmount *ss_mnt,
> goto out;
> }
>
> + if (S_ISDIR(fattr->mode)) {
> + res = ERR_PTR(-EBADF);
> + goto out;
> + }
> +

Can we also enhance nfsd4_do_async_copy to check for
-EBADF and returns nfserr_wrong_type? perhaps adding
an error mapping function to handle other errors also.

-Dai

> res = ERR_PTR(-ENOMEM);
> len = strlen(SSC_READ_NAME_BODY) + 16;
> read_name = kzalloc(len, GFP_KERNEL);
> @@ -357,6 +362,7 @@ static struct file *__nfs42_ssc_open(struct
> vfsmount *ss_mnt,
> r_ino->i_fop);
> if (IS_ERR(filep)) {
> res = ERR_CAST(filep);
> + iput(r_ino);
> goto out_free_name;
> }