NFS: Fix access to suid/sgid executables

nfs_open_permission_mask() should only check MAY_EXEC for files that
are opened with __FMODE_EXEC.

Also fix NFSv4 access-in-open path in a similar way -- openflags must be
used because fmode will not always have FMODE_EXEC set.

This patch fixes https://bugzilla.kernel.org/show_bug.cgi?id=49101

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org

1 files changed, 11 insertions, 7 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 5d864fb36578..cf747ef86650 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1626,7 +1626,8 @@ static int _nfs4_recover_proc_open(struct nfs4_opendata *data)
 
 static int nfs4_opendata_access(struct rpc_cred *cred,
                                 struct nfs4_opendata *opendata,
-                                struct nfs4_state *state, fmode_t fmode)
+                                struct nfs4_state *state, fmode_t fmode,
+                                int openflags)
 {
         struct nfs_access_entry cache;
         u32 mask;
@@ -1638,11 +1639,14 @@ static int nfs4_opendata_access(struct rpc_cred *cred,
 
         mask = 0;
         /* don't check MAY_WRITE - a newly created file may not have
-         * write mode bits, but POSIX allows the creating process to write */
-        if (fmode & FMODE_READ)
-                mask |= MAY_READ;
-        if (fmode & FMODE_EXEC)
-                mask |= MAY_EXEC;
+         * write mode bits, but POSIX allows the creating process to write.
+         * use openflags to check for exec, because fmode won't
+         * always have FMODE_EXEC set when file open for exec. */
+        if (openflags & __FMODE_EXEC) {
+                /* ONLY check for exec rights */
+                mask = MAY_EXEC;
+        } else if (fmode & FMODE_READ)
+                mask = MAY_READ;
 
         cache.cred = cred;
         cache.jiffies = jiffies;
@@ -1896,7 +1900,7 @@ static int _nfs4_do_open(struct inode *dir,
         if (server->caps & NFS_CAP_POSIX_LOCK)
                 set_bit(NFS_STATE_POSIX_LOCKS, &state->flags);
 
-        status = nfs4_opendata_access(cred, opendata, state, fmode);
+        status = nfs4_opendata_access(cred, opendata, state, fmode, flags);
         if (status != 0)
                 goto err_opendata_put;