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Implement a new open(2) flag: O_NOFOLLOW. This will instruct open

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to not follow symlinks, but to open a handle on the link itself(!).
As strange as this might sound, it has several useful applications
safe race-free ways of opening files in hostile areas (eg: /tmp, a mode
1777 /var/mail, etc).  It also would allow things like fchown() to work
on the link rather than having to implement a new syscall specifically for
that task.

Reviewed by: phk
This commit is contained in:
Peter Wemm 1998-04-06 17:38:43 +00:00
parent eb1c943900
commit 7e3426aa1f
2 changed files with 5 additions and 3 deletions
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5
sys/kern/vfs_vnops.c
View File

@ -36,7 +36,7 @@
* SUCH DAMAGE.
*
* @(#)vfs_vnops.c 8.2 (Berkeley) 1/21/94
* $Id: vfs_vnops.c,v 1.49 1998/02/06 12:13:33 eivind Exp $
* $Id: vfs_vnops.c,v 1.50 1998/02/25 05:58:47 bde Exp $
*/
#include <sys/param.h>
@ -118,7 +118,8 @@ vn_open(ndp, fmode, cmode)
}
} else {
ndp->ni_cnd.cn_nameiop = LOOKUP;
ndp->ni_cnd.cn_flags = FOLLOW | LOCKLEAF;
ndp->ni_cnd.cn_flags =
((fmode & O_NOFOLLOW) ? NOFOLLOW : FOLLOW) | LOCKLEAF;
error = namei(ndp);
if (error)
return (error);

3
sys/sys/fcntl.h
View File

@ -36,7 +36,7 @@
* SUCH DAMAGE.
*
* @(#)fcntl.h 8.3 (Berkeley) 1/21/94
* $Id$
* $Id: fcntl.h,v 1.6 1997/02/22 09:45:13 peter Exp $
*/
#ifndef _SYS_FCNTL_H_
@ -84,6 +84,7 @@
#define O_EXLOCK 0x0020 /* open with exclusive file lock */
#define O_ASYNC 0x0040 /* signal pgrp when data ready */
#define O_FSYNC 0x0080 /* synchronous writes */
#define O_NOFOLLOW 0x0100 /* don't follow symlinks */
#endif
#define O_CREAT 0x0200 /* create if nonexistent */
#define O_TRUNC 0x0400 /* truncate to zero length */