ACK: [SRU Focal:oem-5.6] nfsd: apply umask on fs without ACL support

[Colin Ian King]

On 09/09/2020 20:21, Thadeu Lima de Souza Cascardo wrote:
> From: "J. Bruce Fields" <bfields at redhat.com>
> 
> The server is failing to apply the umask when creating new objects on
> filesystems without ACL support.
> 
> To reproduce this, you need to use NFSv4.2 and a client and server
> recent enough to support umask, and you need to export a filesystem that
> lacks ACL support (for example, ext4 with the "noacl" mount option).
> 
> Filesystems with ACL support are expected to take care of the umask
> themselves (usually by calling posix_acl_create).
> 
> For filesystems without ACL support, this is up to the caller of
> vfs_create(), vfs_mknod(), or vfs_mkdir().
> 
> Reported-by: Elliott Mitchell <ehem+debian at m5p.com>
> Reported-by: Salvatore Bonaccorso <carnil at debian.org>
> Tested-by: Salvatore Bonaccorso <carnil at debian.org>
> Fixes: 47057abde515 ("nfsd: add support for the umask attribute")
> Cc: stable at vger.kernel.org
> Signed-off-by: J. Bruce Fields <bfields at redhat.com>
> (cherry picked from commit 22cf8419f1319ff87ec759d0ebdff4cbafaee832)
> CVE-2020-24394
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
> ---
>  fs/nfsd/vfs.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 0aa02eb18bd3..8fa3e0ff3671 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1225,6 +1225,9 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  		iap->ia_mode = 0;
>  	iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;
>  
> +	if (!IS_POSIXACL(dirp))
> +		iap->ia_mode &= ~current_umask();
> +
>  	err = 0;
>  	host_err = 0;
>  	switch (type) {
> @@ -1457,6 +1460,9 @@ do_nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  		goto out;
>  	}
>  
> +	if (!IS_POSIXACL(dirp))
> +		iap->ia_mode &= ~current_umask();
> +
>  	host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
>  	if (host_err < 0) {
>  		fh_drop_write(fhp);
> 

Clean cherry pick, looks fine to me.

Acked-by: Colin Ian King <colin.king at canonical.com>