linux-kernel - [PATCHv5 3/7] binfmt_misc: use get_unused_fd_flags(0) instead of get_unused

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Message-Id: <c2bc1bfaabdb2b1ac207037550bc61e656938b97.1388952061.git.ydroneaud@opteya.com>
Date:	Sun,  5 Jan 2014 21:36:30 +0100
From:	Yann Droneaud <ydroneaud@...eya.com>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Yann Droneaud <ydroneaud@...eya.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCHv5 3/7] binfmt_misc: use get_unused_fd_flags(0) instead of get_unused_fd()

Macro get_unused_fd() is used to allocate a file descriptor with
default flags. Those default flags (0) can be "unsafe":
O_CLOEXEC must be used by default to not leak file descriptor
across exec().

Instead of macro get_unused_fd(), function get_unused_fd_flags()
(or anon_inode_getfd()) should be used with flags given by userspace.
If not possible, flags should be set to O_CLOEXEC to provide userspace
with a default safe behavor.

In a further patch, get_unused_fd() will be removed so that new code
start using get_unused_fd_flags() (or anon_inode_getfd()) with correct
flags.

This patch replaces calls to get_unused_fd() with equivalent call to
get_unused_fd_flags(0) to preserve current behavor for existing code.

The hard coded flag value (0) should be reviewed on a per-subsystem
basis, and, if possible, set to O_CLOEXEC.

Cc: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Yann Droneaud <ydroneaud@...eya.com>
Link: http://lkml.kernel.org/r/cover.1388952061.git.ydroneaud@opteya.com
---
 fs/binfmt_misc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 1c740e152f38..052f6dc8e549 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -138,7 +138,7 @@ static int load_misc_binary(struct linux_binprm *bprm)
 		/* if the binary should be opened on behalf of the
 		 * interpreter than keep it open and assign descriptor
 		 * to it */
- 		fd_binary = get_unused_fd();
+		fd_binary = get_unused_fd_flags(0);
  		if (fd_binary < 0) {
  			retval = fd_binary;
  			goto _ret;
-- 
1.8.4.2

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