[Natty] SRU: nfsd4: permit read opens of executable-only files

[Herton Ronaldo Krzesinski]

On Thu, Dec 15, 2011 at 02:31:39PM -0600, Chris J Arges wrote:
> SRU Justification
> 
> Impact:
> 
> NFSv4 mount point does not allow binary files to run when permissions
> are set to 111.
> 
> Fix:
> 
> Upstream commit a043226bc140a2c1dde162246d68a67e5043e6b2.
> Applies with minor conflicts.
> 
> Testcase:
> Mount a directory using nfsv4. Inside that directory place a binary with
> ---x--x--x permissions. Try to execute the binary. Without this patch it
> will not execute.
> 
> Notes:
> This patch fixes this issue, but requires support from the nfs client as
> well. The Natty version of the client will need additional fixes to
> complete the fix. The upstream maintainer has verified that the kernel
> is doing the right thing. http://comments.gmane.org/gmane.linux.nfs/43028
> 
> Thanks,
> --chris j arges

> From c081b4c32ab604965c4d82438780b967f7c5ad62 Mon Sep 17 00:00:00 2001
> From: "J. Bruce Fields" <bfields at redhat.com>
> Date: Thu, 25 Aug 2011 10:48:39 -0400
> Subject: [PATCH] nfsd4: permit read opens of executable-only files
> 
> A client that wants to execute a file must be able to read it.  Read
> opens over nfs are therefore implicitly allowed for executable files
> even when those files are not readable.
> 
> NFSv2/v3 get this right by using a passed-in NFSD_MAY_OWNER_OVERRIDE on
> read requests, but NFSv4 has gotten this wrong ever since
> dc730e173785e29b297aa605786c94adaffe2544 "nfsd4: fix owner-override on
> open", when we realized that the file owner shouldn't override
> permissions on non-reclaim NFSv4 opens.
> 
> So we can't use NFSD_MAY_OWNER_OVERRIDE to tell nfsd_permission to allow
> reads of executable files.
> 
> So, do the same thing we do whenever we encounter another weird NFS
> permission nit: define yet another NFSD_MAY_* flag.
> 
> The industry's future standardization on 128-bit processors will be
> motivated primarily by the need for integers with enough bits for all
> the NFSD_MAY_* flags.
> 
> Reported-by: Leonardo Borda <leonardoborda at gmail.com>
> Cc: stable at kernel.org
> Signed-off-by: J. Bruce Fields <bfields at redhat.com>
> (cherry picked from commit a043226bc140a2c1dde162246d68a67e5043e6b2)
> 
> BugLink: http://bugs.launchpad.net/bugs/833300
> 
> Conflicts:
> 
> 	fs/nfsd/vfs.h
> 
> Signed-off-by: Chris J Arges <chris.j.arges at canonical.com>
> ---
>  fs/nfsd/nfs4proc.c |    2 ++
>  fs/nfsd/vfs.c      |    3 ++-
>  fs/nfsd/vfs.h      |    2 ++
>  3 files changed, 6 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 5fcb139..2df5614 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -156,6 +156,8 @@ do_open_permission(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfs
>  		!(open->op_share_access & NFS4_SHARE_ACCESS_WRITE))
>  		return nfserr_inval;
>  
> +	accmode |= NFSD_MAY_READ_IF_EXEC;
> +
>  	if (open->op_share_access & NFS4_SHARE_ACCESS_READ)
>  		accmode |= NFSD_MAY_READ;
>  	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE)
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 435f407..f0ee82a 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -2104,7 +2104,8 @@ nfsd_permission(struct svc_rqst *rqstp, struct svc_export *exp,
>  
>  	/* Allow read access to binaries even when mode 111 */
>  	if (err == -EACCES && S_ISREG(inode->i_mode) &&
> -	    acc == (NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE))
> +	     (acc == (NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE) ||
> +	      acc == (NFSD_MAY_READ | NFSD_MAY_READ_IF_EXEC)))
>  		err = inode_permission(inode, MAY_EXEC);
>  
>  	return err? nfserrno(err) : 0;
> diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
> index 9a370a5..dbe9ac1 100644
> --- a/fs/nfsd/vfs.h
> +++ b/fs/nfsd/vfs.h
> @@ -21,6 +21,8 @@
>  #define NFSD_MAY_LOCAL_ACCESS	128 /* IRIX doing local access check on device special file*/
>  #define NFSD_MAY_BYPASS_GSS_ON_ROOT 256
>  #define NFSD_MAY_NOT_BREAK_LEASE 512
> +#define NFSD_MAY_BYPASS_GSS	1024
> +#define NFSD_MAY_READ_IF_EXEC	2048

Any reason to also add NFSD_MAY_BYPASS_GSS?

Also may be it would be good to settle the client situation on natty
before, as the patch will not help currently.

>  
>  #define NFSD_MAY_CREATE		(NFSD_MAY_EXEC|NFSD_MAY_WRITE)
>  #define NFSD_MAY_REMOVE		(NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC)
> -- 
> 1.7.5.4
> 

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