[PATCHv8 6/6] file: remove get_unused_fd() macro

From: Yann Droneaud
Date: Wed Sep 24 2014 - 13:51:15 EST

Macro get_unused_fd() is used to allocate a file descriptor
with default flags. Those default flags (0) don't enable

This can be seen as an unsafe default: in most case close-on-exec
should be enabled to not leak file descriptor across exec().

It would be better to have a "safer" default set of flags, eg.
O_CLOEXEC must be used to enable close-on-exec.

Instead this patch removes get_unused_fd() so that out of tree
modules won't be affect by a runtime behavor change which might
introduce other kind of bugs: it's better to catch the change at
build time, making it easier to fix.

Removing the macro will also promote use of get_unused_fd_flags()
(or anon_inode_getfd()) with flags provided by userspace. Or, if
flags cannot be given by userspace, with flags set to O_CLOEXEC
by default.

Link: http://lkml.kernel.org/r/cover.1411562410.git.ydroneaud@xxxxxxxxxx
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx>
include/linux/file.h | 1 -
1 file changed, 1 deletion(-)

diff --git a/include/linux/file.h b/include/linux/file.h
index 4d69123377a2..f87d30882a24 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -66,7 +66,6 @@ extern void set_close_on_exec(unsigned int fd, int flag);
extern bool get_close_on_exec(unsigned int fd);
extern void put_filp(struct file *);
extern int get_unused_fd_flags(unsigned flags);
-#define get_unused_fd() get_unused_fd_flags(0)
extern void put_unused_fd(unsigned int fd);

extern void fd_install(unsigned int fd, struct file *file);

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