nfsd4: permit read opens of executable-only files

Commit Message

J. Bruce Fields Aug. 25, 2011, 4:19 p.m. UTC

From: J. Bruce Fields <[e-mail]>

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 <[e-mail]>
Cc: [e-mail]
Signed-off-by: J. Bruce Fields <[e-mail]>
---
 fs/nfsd/nfs4proc.c |    2 ++
 fs/nfsd/vfs.c      |    3 ++-
 fs/nfsd/vfs.h      |    1 +
 3 files changed, 5 insertions(+), 1 deletions(-)

Comments

Jim Rees Aug. 25, 2011, 5:31 p.m. UTC | #1

J. Bruce Fields wrote:

   #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

Not the fault of your patch, but it seems odd, unreadable, and error-prone
that these flag bits are defined in terms of base-10 numbers.
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Patch

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index d30253a..3fb07ac 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 4c22870..75c35fa 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -2116,7 +2116,8 @@  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 e0bbac0..a22e40e 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -25,6 +25,7 @@ 
 #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
 
 #define NFSD_MAY_CREATE		(NFSD_MAY_EXEC|NFSD_MAY_WRITE)
 #define NFSD_MAY_REMOVE		(NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC)