VFS: Fix access("file", X_OK) in the presence of ACLs

Currently, the access() call will return incorrect information on NFS if
there exists an ACL that grants execute access to the user on a regular
file. The reason the information is incorrect is that the VFS overrides
this execute access in open_exec() by checking (inode->i_mode & 0111).

This patch propagates the VFS execute bit check back into the generic
permission() call.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
(cherry picked from 64cbae98848c4c99851cb0a405f0b4982cd76c1e commit)

diff --git a/fs/namei.c b/fs/namei.c
index 8631664..432d6bc 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -227,10 +227,10 @@ int generic_permission(struct inode *inode, int mask,
 
 int permission(struct inode *inode, int mask, struct nameidata *nd)
 {
+       umode_t mode = inode->i_mode;
        int retval, submask;
 
        if (mask & MAY_WRITE) {
-               umode_t mode = inode->i_mode;
 
                /*
                 * Nobody gets write access to a read-only fs.
@@ -247,6 +247,13 @@ int permission(struct inode *inode, int mask, struct nameidata *nd)
        }
 
 
+       /*
+        * MAY_EXEC on regular files requires special handling: We override
+        * filesystem execute permissions if the mode bits aren't set.
+        */
+       if ((mask & MAY_EXEC) && S_ISREG(mode) && !(mode & S_IXUGO))
+               return -EACCES;
+
        /* Ordinary permission routines do not understand MAY_APPEND. */
        submask = mask & ~MAY_APPEND;
        if (inode->i_op && inode->i_op->permission)