Re: [PATCH 2/2] dFrom: Max Kellermann <m...@cm4all.com>

[Trond Myklebust]

On Mon, 2018-01-15 at 18:30 +0100, Max Kellermann wrote:
> nfs/super: set MS_POSIXACL only if ACL support is enabled
> 
> The code comment says "We will [apply the umask] ourselves", but that
> happens in posix_acl_create() only if the kernel has POSIX ACL
> support.  Without it, posix_acl_create() is a is an empty dummy
> function.
> 
> So let's not pretend we will apply the umask if we can already know
> that we will never.
> 
> This fixes a problem where the umask is always ignored in the NFS
> client when compiled without CONFIG_FS_POSIX_ACL.  This is a 4 year
> old regression caused by commit 013cdf1088d723 which itself was not
> completely wrong, but failed to consider all the side effects by
> misdesigned VFS code.
> 
> There are two compile-time checks and one runtime check:
> 
> - If CONFIG_FS_POSIX_ACL=n, then MS_POSIXACL is never set.
> 
> - If CONFIG_FS_POSIX_ACL=y and CONFIG_NFS_V3_ACL=n, then only NFSv4
>   has ACL support (and cannot be disabled), and we need to check for
>   "version==4".
> 
> - If CONFIG_FS_POSIX_ACL=y and CONFIG_NFS_V3_ACL=y, MS_POSIXACL is
>   always set, as before.
> 
> Signed-off-by: Max Kellermann 
> ---
>  fs/nfs/super.c |   15 +++
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index 216f67d628b3..ec4e1f2775e0 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -2338,10 +2338,17 @@ void nfs_fill_super(struct super_block *sb,
> struct nfs_mount_info *mount_info)
>   sb->s_blocksize = nfs_block_size(data->bsize, 
> >s_blocksize_bits);
>  
>   if (server->nfs_client->rpc_ops->version != 2) {
> - /* The VFS shouldn't apply the umask to mode bits.
> We will do
> -  * so ourselves when necessary.
> -  */
> - sb->s_flags |= MS_POSIXACL;
> +#ifdef CONFIG_FS_POSIX_ACL
> +#ifndef CONFIG_NFS_V3_ACL
> + if (nfss->nfs_client->rpc_ops->version == 4)
> +#endif
> + /* The VFS shouldn't apply the umask to mode
> +  * bits. We will do so ourselves when
> +  * necessary.
> +  */
> + sb->s_flags |= MS_POSIXACL;
> +#endif
> +
>   sb->s_time_gran = 1;
>   sb->s_export_op = _export_ops;
>   }

The above illustrates exactly why I've asked people _never_ to make
anything conditional on rpc_ops->version. Please use a NFS capability
(i.e. NFS_SB(sb)->caps) for this kind of thing. That expresses the
condition in terms of the functionality we want instead of a whimsical
protocol version number.

Thanks
  Trond
-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.mykleb...@primarydata.com

Re: [PATCH 2/2] dFrom: Max Kellermann <m...@cm4all.com>

[Max Kellermann]

On 2018/01/15 18:41, Greg KH  wrote:
> Your subject line is a bit odd :(

True, I already repaired & resent it.  Sorry for the hiccup.

Re: [PATCH 2/2] dFrom: Max Kellermann <m...@cm4all.com>

[Greg KH]

On Mon, Jan 15, 2018 at 06:30:51PM +0100, Max Kellermann wrote:
> nfs/super: set MS_POSIXACL only if ACL support is enabled
> 
> The code comment says "We will [apply the umask] ourselves", but that
> happens in posix_acl_create() only if the kernel has POSIX ACL
> support.  Without it, posix_acl_create() is a is an empty dummy
> function.



Your subject line is a bit odd :(

[PATCH 2/2] dFrom: Max Kellermann <m...@cm4all.com>

[Max Kellermann]

nfs/super: set MS_POSIXACL only if ACL support is enabled

The code comment says "We will [apply the umask] ourselves", but that
happens in posix_acl_create() only if the kernel has POSIX ACL
support.  Without it, posix_acl_create() is a is an empty dummy
function.

So let's not pretend we will apply the umask if we can already know
that we will never.

This fixes a problem where the umask is always ignored in the NFS
client when compiled without CONFIG_FS_POSIX_ACL.  This is a 4 year
old regression caused by commit 013cdf1088d723 which itself was not
completely wrong, but failed to consider all the side effects by
misdesigned VFS code.

There are two compile-time checks and one runtime check:

- If CONFIG_FS_POSIX_ACL=n, then MS_POSIXACL is never set.

- If CONFIG_FS_POSIX_ACL=y and CONFIG_NFS_V3_ACL=n, then only NFSv4
  has ACL support (and cannot be disabled), and we need to check for
  "version==4".

- If CONFIG_FS_POSIX_ACL=y and CONFIG_NFS_V3_ACL=y, MS_POSIXACL is
  always set, as before.

Signed-off-by: Max Kellermann 
---
 fs/nfs/super.c |   15 +++
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 216f67d628b3..ec4e1f2775e0 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2338,10 +2338,17 @@ void nfs_fill_super(struct super_block *sb, struct 
nfs_mount_info *mount_info)
sb->s_blocksize = nfs_block_size(data->bsize, 
>s_blocksize_bits);
 
if (server->nfs_client->rpc_ops->version != 2) {
-   /* The VFS shouldn't apply the umask to mode bits. We will do
-* so ourselves when necessary.
-*/
-   sb->s_flags |= MS_POSIXACL;
+#ifdef CONFIG_FS_POSIX_ACL
+#ifndef CONFIG_NFS_V3_ACL
+   if (nfss->nfs_client->rpc_ops->version == 4)
+#endif
+   /* The VFS shouldn't apply the umask to mode
+* bits. We will do so ourselves when
+* necessary.
+*/
+   sb->s_flags |= MS_POSIXACL;
+#endif
+
sb->s_time_gran = 1;
sb->s_export_op = _export_ops;
}