fix execute checking in permission()

permission() checks that MAY_EXEC is only allowed on regular files if at least
one execute bit is set in the file mode.

generic_permission() already ensures this, so the extra check in permission()
is superfluous.

If the filesystem defines it's own ->permission() the check may still be
needed.  In this case move it after ->permission().  This is needed because
filesystems such as FUSE may need to refresh the inode attributes before
checking permissions.

This check should be moved inside ->permission(), but that's another story.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/namei.c b/fs/namei.c
index 7cba63295a82f4aec85e0ce1f52c9f0fb9bbc8d7..2792e0ca01d4f03effa44a304e477da9b5e706c0 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.
@@ -246,22 +246,34 @@ int permission(struct inode *inode, int mask, struct nameidata *nd)
                        return -EACCES;
        }
 
-
-       /*
-        * MAY_EXEC on regular files requires special handling: We override
-        * filesystem execute permissions if the mode bits aren't set or
-        * the fs is mounted with the "noexec" flag.
-        */
-       if ((mask & MAY_EXEC) && S_ISREG(mode) && (!(mode & S_IXUGO) ||
-                       (nd && nd->mnt && (nd->mnt->mnt_flags & MNT_NOEXEC))))
-               return -EACCES;
+       if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) {
+               /*
+                * MAY_EXEC on regular files is denied if the fs is mounted
+                * with the "noexec" flag.
+                */
+               if (nd && nd->mnt && (nd->mnt->mnt_flags & MNT_NOEXEC))
+                       return -EACCES;
+       }
 
        /* Ordinary permission routines do not understand MAY_APPEND. */
        submask = mask & ~MAY_APPEND;
-       if (inode->i_op && inode->i_op->permission)
+       if (inode->i_op && inode->i_op->permission) {
                retval = inode->i_op->permission(inode, submask, nd);
-       else
+               if (!retval) {
+                       /*
+                        * Exec permission on a regular file is denied if none
+                        * of the execute bits are set.
+                        *
+                        * This check should be done by the ->permission()
+                        * method.
+                        */
+                       if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode) &&
+                           !(inode->i_mode & S_IXUGO))
+                               return -EACCES;
+               }
+       } else {
                retval = generic_permission(inode, submask, NULL);
+       }
        if (retval)
                return retval;