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As discussed on tech-kern: 

Factor out common code of chroot-like syscalls into change_root() and export
that function for use in other parts of the kernel.
Rename change_dir() to chdir_lookup() as the latter describes better what
the function does.  While there, move the namei_data initialisation into
chdir_lookup(), too.  And export chdir_lookup().
This commit is contained in:
bad 2009-08-01 21:17:11 +00:00
parent d582bd909a
commit 02bcf17298
2 changed files with 38 additions and 51 deletions
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84
sys/kern/vfs_syscalls.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: vfs_syscalls.c,v 1.396 2009/07/02 12:53:47 pooka Exp $ */ /* $NetBSD: vfs_syscalls.c,v 1.397 2009/08/01 21:17:11 bad Exp $ */
/*- /*-
* Copyright (c) 2008, 2009 The NetBSD Foundation, Inc. * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@ -66,7 +66,7 @@
*/ */
#include <sys/cdefs.h> #include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_syscalls.c,v 1.396 2009/07/02 12:53:47 pooka Exp $"); __KERNEL_RCSID(0, "$NetBSD: vfs_syscalls.c,v 1.397 2009/08/01 21:17:11 bad Exp $");
#ifdef _KERNEL_OPT #ifdef _KERNEL_OPT
#include "opt_fileassoc.h" #include "opt_fileassoc.h"
@ -110,7 +110,6 @@ __KERNEL_RCSID(0, "$NetBSD: vfs_syscalls.c,v 1.396 2009/07/02 12:53:47 pooka Exp
MALLOC_DEFINE(M_MOUNT, "mount", "vfs mount struct"); MALLOC_DEFINE(M_MOUNT, "mount", "vfs mount struct");
static int change_dir(struct nameidata *, struct lwp *);
static int change_flags(struct vnode *, u_long, struct lwp *); static int change_flags(struct vnode *, u_long, struct lwp *);
static int change_mode(struct vnode *, int, struct lwp *l); static int change_mode(struct vnode *, int, struct lwp *l);
static int change_owner(struct vnode *, uid_t, gid_t, struct lwp *, int); static int change_owner(struct vnode *, uid_t, gid_t, struct lwp *, int);
@ -1126,7 +1125,6 @@ int
sys_fchroot(struct lwp *l, const struct sys_fchroot_args *uap, register_t *retval) sys_fchroot(struct lwp *l, const struct sys_fchroot_args *uap, register_t *retval)
{ {
struct proc *p = l->l_proc; struct proc *p = l->l_proc;
struct cwdinfo *cwdi;
struct vnode *vp; struct vnode *vp;
file_t *fp; file_t *fp;
int error, fd = SCARG(uap, fd); int error, fd = SCARG(uap, fd);
@ -1135,7 +1133,7 @@ sys_fchroot(struct lwp *l, const struct sys_fchroot_args *uap, register_t *retva
KAUTH_REQ_SYSTEM_CHROOT_FCHROOT, NULL, NULL, NULL)) != 0) KAUTH_REQ_SYSTEM_CHROOT_FCHROOT, NULL, NULL, NULL)) != 0)
return error; return error;
/* fd_getvnode() will use the descriptor for us */ /* fd_getvnode() will use the descriptor for us */
if ((error = fd_getvnode(SCARG(uap, fd), &fp)) != 0) if ((error = fd_getvnode(fd, &fp)) != 0)
return error; return error;
vp = fp->f_data; vp = fp->f_data;
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
@ -1148,27 +1146,7 @@ sys_fchroot(struct lwp *l, const struct sys_fchroot_args *uap, register_t *retva
goto out; goto out;
VREF(vp); VREF(vp);
/* change_root(p->p_cwdi, vp, l);
* Prevent escaping from chroot by putting the root under
* the working directory. Silently chdir to / if we aren't
* already there.
*/
cwdi = p->p_cwdi;
rw_enter(&cwdi->cwdi_lock, RW_WRITER);
if (!vn_isunder(cwdi->cwdi_cdir, vp, l)) {
/*
* XXX would be more failsafe to change directory to a
* deadfs node here instead
*/
vrele(cwdi->cwdi_cdir);
VREF(vp);
cwdi->cwdi_cdir = vp;
}
if (cwdi->cwdi_rdir != NULL)
vrele(cwdi->cwdi_rdir);
cwdi->cwdi_rdir = vp;
rw_exit(&cwdi->cwdi_lock);
out: out:
fd_putfile(fd); fd_putfile(fd);
@ -1188,16 +1166,15 @@ sys_chdir(struct lwp *l, const struct sys_chdir_args *uap, register_t *retval)
struct proc *p = l->l_proc; struct proc *p = l->l_proc;
struct cwdinfo *cwdi; struct cwdinfo *cwdi;
int error; int error;
struct nameidata nd; struct vnode *vp;
NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | TRYEMULROOT, UIO_USERSPACE, if ((error = chdir_lookup(SCARG(uap, path), UIO_USERSPACE,
SCARG(uap, path)); &vp, l)) != 0)
if ((error = change_dir(&nd, l)) != 0)
return (error); return (error);
cwdi = p->p_cwdi; cwdi = p->p_cwdi;
rw_enter(&cwdi->cwdi_lock, RW_WRITER); rw_enter(&cwdi->cwdi_lock, RW_WRITER);
vrele(cwdi->cwdi_cdir); vrele(cwdi->cwdi_cdir);
cwdi->cwdi_cdir = nd.ni_vp; cwdi->cwdi_cdir = vp;
rw_exit(&cwdi->cwdi_lock); rw_exit(&cwdi->cwdi_lock);
return (0); return (0);
} }
@ -1213,24 +1190,31 @@ sys_chroot(struct lwp *l, const struct sys_chroot_args *uap, register_t *retval)
syscallarg(const char *) path; syscallarg(const char *) path;
} */ } */
struct proc *p = l->l_proc; struct proc *p = l->l_proc;
struct cwdinfo *cwdi;
struct vnode *vp;
int error; int error;
struct nameidata nd; struct vnode *vp;
if ((error = kauth_authorize_system(l->l_cred, KAUTH_SYSTEM_CHROOT, if ((error = kauth_authorize_system(l->l_cred, KAUTH_SYSTEM_CHROOT,
KAUTH_REQ_SYSTEM_CHROOT_CHROOT, NULL, NULL, NULL)) != 0) KAUTH_REQ_SYSTEM_CHROOT_CHROOT, NULL, NULL, NULL)) != 0)
return (error); return (error);
NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | TRYEMULROOT, UIO_USERSPACE, if ((error = chdir_lookup(SCARG(uap, path), UIO_USERSPACE,
SCARG(uap, path)); &vp, l)) != 0)
if ((error = change_dir(&nd, l)) != 0)
return (error); return (error);
cwdi = p->p_cwdi; change_root(p->p_cwdi, vp, l);
return (0);
}
/*
* Common routine for chroot and fchroot.
*/
void
change_root(struct cwdinfo *cwdi, struct vnode *vp, struct lwp *l)
{
rw_enter(&cwdi->cwdi_lock, RW_WRITER); rw_enter(&cwdi->cwdi_lock, RW_WRITER);
if (cwdi->cwdi_rdir != NULL) if (cwdi->cwdi_rdir != NULL)
vrele(cwdi->cwdi_rdir); vrele(cwdi->cwdi_rdir);
vp = nd.ni_vp;
cwdi->cwdi_rdir = vp; cwdi->cwdi_rdir = vp;
/* /*
@ -1248,31 +1232,31 @@ sys_chroot(struct lwp *l, const struct sys_chroot_args *uap, register_t *retval)
cwdi->cwdi_cdir = vp; cwdi->cwdi_cdir = vp;
} }
rw_exit(&cwdi->cwdi_lock); rw_exit(&cwdi->cwdi_lock);
return (0);
} }
/* /*
* Common routine for chroot and chdir. * Common routine for chroot and chdir.
*/ */
static int int
change_dir(struct nameidata *ndp, struct lwp *l) chdir_lookup(const char *path, int where, struct vnode **vpp, struct lwp *l)
{ {
struct vnode *vp; struct nameidata nd;
int error; int error;
if ((error = namei(ndp)) != 0) NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | TRYEMULROOT, where,
path);
if ((error = namei(&nd)) != 0)
return (error); return (error);
vp = ndp->ni_vp; *vpp = nd.ni_vp;
if (vp->v_type != VDIR) if ((*vpp)->v_type != VDIR)
error = ENOTDIR; error = ENOTDIR;
else else
error = VOP_ACCESS(vp, VEXEC, l->l_cred); error = VOP_ACCESS(*vpp, VEXEC, l->l_cred);
if (error) if (error)
vput(vp); vput(*vpp);
else else
VOP_UNLOCK(vp, 0); VOP_UNLOCK(*vpp, 0);
return (error); return (error);
} }

5
sys/sys/vfs_syscalls.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: vfs_syscalls.h,v 1.11 2009/07/02 12:56:40 pooka Exp $ */ /* $NetBSD: vfs_syscalls.h,v 1.12 2009/08/01 21:17:12 bad Exp $ */
/* /*
* Copyright (c) 2007, 2008, 2009 The NetBSD Foundation, Inc. * Copyright (c) 2007, 2008, 2009 The NetBSD Foundation, Inc.
@ -65,4 +65,7 @@ int do_sys_rename(const char *, const char *, enum uio_seg, int);
int do_sys_mknod(struct lwp *l, const char *, mode_t, dev_t, register_t *); int do_sys_mknod(struct lwp *l, const char *, mode_t, dev_t, register_t *);
int do_sys_mkdir(const char *, mode_t); int do_sys_mkdir(const char *, mode_t);
int chdir_lookup(const char *, int, struct vnode **, struct lwp *);
void change_root(struct cwdinfo *, struct vnode *, struct lwp *);
#endif /* _SYS_VFS_SYSCALLS_H_ */ #endif /* _SYS_VFS_SYSCALLS_H_ */