linux-kernel - [PATCHv9 5/5] file: remove get_unused

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Message-Id: <63799031ab6a617b3d435e240de54fafef1ba66d.1413223900.git.ydroneaud@opteya.com>
Date:	Thu, 21 Mar 2013 00:23:53 +0100
From:	Yann Droneaud <ydroneaud@...eya.com>
To:	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCHv9 5/5] file: remove get_unused_fd() macro

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

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.1413223900.git.ydroneaud@opteya.com
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Yann Droneaud <ydroneaud@...eya.com>
---
 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);
-- 
1.9.3

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