file: simplify logic in __close_range()

It never looked too pleasant and it doesn't really buy us anything
anymore now that CLOSE_RANGE_CLOEXEC exists and we need to retake the
current maximum under the lock for it anyway. This also makes the logic
easier to follow.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Giuseppe Scrivano <gscrivan@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/fs/file.c b/fs/file.c
index 7400403..ed46cd3 100644 (file)
--- a/fs/file.c
+++ b/fs/file.c
@@ -701,7 +701,6 @@ static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
  */
 int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
 {
-       unsigned int cur_max;
        struct task_struct *me = current;
        struct files_struct *cur_fds = me->files, *fds = NULL;
 
@@ -711,26 +710,26 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
        if (fd > max_fd)
                return -EINVAL;
 
-       rcu_read_lock();
-       cur_max = files_fdtable(cur_fds)->max_fds;
-       rcu_read_unlock();
-
-       /* cap to last valid index into fdtable */
-       cur_max--;
-
        if (flags & CLOSE_RANGE_UNSHARE) {
                int ret;
                unsigned int max_unshare_fds = NR_OPEN_MAX;
 
                /*
-                * If the requested range is greater than the current maximum,
-                * we're closing everything so only copy all file descriptors
-                * beneath the lowest file descriptor.
-                * If the caller requested all fds to be made cloexec copy all
-                * of the file descriptors since they still want to use them.
+                * If the caller requested all fds to be made cloexec we always
+                * copy all of the file descriptors since they still want to
+                * use them.
                 */
-               if (!(flags & CLOSE_RANGE_CLOEXEC) && (max_fd >= cur_max))
-                       max_unshare_fds = fd;
+               if (!(flags & CLOSE_RANGE_CLOEXEC)) {
+                       /*
+                        * If the requested range is greater than the current
+                        * maximum, we're closing everything so only copy all
+                        * file descriptors beneath the lowest file descriptor.
+                        */
+                       rcu_read_lock();
+                       if (max_fd >= last_fd(files_fdtable(cur_fds)))
+                               max_unshare_fds = fd;
+                       rcu_read_unlock();
+               }
 
                ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
                if (ret)
@@ -744,8 +743,6 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
                        swap(cur_fds, fds);
        }
 
-       max_fd = min(max_fd, cur_max);
-
        if (flags & CLOSE_RANGE_CLOEXEC)
                __range_cloexec(cur_fds, fd, max_fd);
        else