[PATCH 5.11 06/36] fs: provide locked helper variant of close_fd_get_file()

gregkh
2021-03-10T13:25:12Z

From: Jens Axboe <axboe@kernel.dk>

commit 53dec2ea74f2ef360e8455439be96a780baa6097 upstream

Assumes current->files->file_lock is already held on invocation. Helps
the caller check the file before removing the fd, if it needs to.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/file.c | 36 +++++++++++++++++++++++++-----------
fs/internal.h | 1 +
2 files changed, 26 insertions(+), 11 deletions(-)

--- a/fs/file.c
+++ b/fs/file.c
@@ -22,6 +22,8 @@
#include <linux/close_range.h>
#include <net/sock.h>

+#include "internal.h"
+
unsigned int sysctl_nr_open __read_mostly = 1024*1024;
unsigned int sysctl_nr_open_min = BITS_PER_LONG;
/* our min() is unusable in constant expressions ;-/ */
@@ -732,36 +734,48 @@ int __close_range(unsigned fd, unsigned
}

/*
- * variant of close_fd that gets a ref on the file for later fput.
- * The caller must ensure that filp_close() called on the file, and then
- * an fput().
+ * See close_fd_get_file() below, this variant assumes current->files->file_lock
+ * is held.
*/
-int close_fd_get_file(unsigned int fd, struct file **res)
+int __close_fd_get_file(unsigned int fd, struct file **res)
{
struct files_struct *files = current->files;
struct file *file;
struct fdtable *fdt;

- spin_lock(&files->file_lock);
fdt = files_fdtable(files);
if (fd >= fdt->max_fds)
- goto out_unlock;
+ goto out_err;
file = fdt->fd[fd];
if (!file)
- goto out_unlock;
+ goto out_err;
rcu_assign_pointer(fdt->fd[fd], NULL);
__put_unused_fd(files, fd);
- spin_unlock(&files->file_lock);
get_file(file);
*res = file;
return 0;
-
-out_unlock:
- spin_unlock(&files->file_lock);
+out_err:
*res = NULL;
return -ENOENT;
}

+/*
+ * variant of close_fd that gets a ref on the file for later fput.
+ * The caller must ensure that filp_close() called on the file, and then
+ * an fput().
+ */
+int close_fd_get_file(unsigned int fd, struct file **res)
+{
+ struct files_struct *files = current->files;
+ int ret;
+
+ spin_lock(&files->file_lock);
+ ret = __close_fd_get_file(fd, res);
+ spin_unlock(&files->file_lock);
+
+ return ret;
+}
+
void do_close_on_exec(struct files_struct *files)
{
unsigned i;
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -132,6 +132,7 @@ extern struct file *do_file_open_root(st
const char *, const struct open_flags *);
extern struct open_how build_open_how(int flags, umode_t mode);
extern int build_open_flags(const struct open_how *how, struct open_flags *op);
+extern int __close_fd_get_file(unsigned int fd, struct file **res);

long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
int chmod_common(const struct path *path, umode_t mode);