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jail: Change both root and working directories in jail_attach(2)

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jail_attach(2) performs an internal chroot operation, leaving it up to
the calling process to assure the working directory is inside the jail.

Add a matching internal chdir operation to the jail's root.  Also
ignore kern.chroot_allow_open_directories, and always disallow the
operation if there are any directory descriptors open.

Reported by:    mjg
Approved by:    markj, kib
MFC after:      3 days
This commit is contained in:
Jamie Gritton 2021-02-19 14:13:35 -08:00
parent 0f9544d03e
commit d4380c0cdd
4 changed files with 48 additions and 5 deletions
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5
lib/libc/sys/jail.2
View File

@ -25,7 +25,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd February 8, 2012
.Dd February 19, 2021
.Dt JAIL 2
.Os
.Sh NAME
@ -228,6 +228,9 @@ The
system call attaches the current process to an existing jail,
identified by
.Fa jid .
It changes the process's root and current directories to the jail's
.Va path
directory.
.Pp
The
.Fn jail_remove

45
sys/kern/kern_descrip.c
View File

@ -3795,9 +3795,8 @@ pwd_drop(struct pwd *pwd)
}
/*
* Common routine for kern_chroot() and jail_attach(). The caller is
* responsible for invoking priv_check() and mac_vnode_check_chroot() to
* authorize this operation.
* The caller is responsible for invoking priv_check() and
* mac_vnode_check_chroot() to authorize this operation.
*/
int
pwd_chroot(struct thread *td, struct vnode *vp)
@ -3859,6 +3858,46 @@ pwd_chdir(struct thread *td, struct vnode *vp)
pwd_drop(oldpwd);
}
/*
* jail_attach(2) changes both root and working directories.
*/
int
pwd_chroot_chdir(struct thread *td, struct vnode *vp)
{
struct pwddesc *pdp;
struct filedesc *fdp;
struct pwd *newpwd, *oldpwd;
int error;
fdp = td->td_proc->p_fd;
pdp = td->td_proc->p_pd;
newpwd = pwd_alloc();
FILEDESC_SLOCK(fdp);
PWDDESC_XLOCK(pdp);
oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
error = chroot_refuse_vdir_fds(fdp);
FILEDESC_SUNLOCK(fdp);
if (error != 0) {
PWDDESC_XUNLOCK(pdp);
pwd_drop(newpwd);
return (error);
}
vrefact(vp);
newpwd->pwd_rdir = vp;
vrefact(vp);
newpwd->pwd_cdir = vp;
if (oldpwd->pwd_jdir == NULL) {
vrefact(vp);
newpwd->pwd_jdir = vp;
}
pwd_fill(oldpwd, newpwd);
pwd_set(pdp, newpwd);
PWDDESC_XUNLOCK(pdp);
pwd_drop(oldpwd);
return (0);
}
void
pwd_ensure_dirs(void)
{

2
sys/kern/kern_jail.c
View File

@ -2495,7 +2495,7 @@ do_jail_attach(struct thread *td, struct prison *pr)
goto e_unlock;
#endif
VOP_UNLOCK(pr->pr_root);
if ((error = pwd_chroot(td, pr->pr_root)))
if ((error = pwd_chroot_chdir(td, pr->pr_root)))
goto e_revert_osd;
newcred = crget();

1
sys/sys/filedesc.h
View File

@ -333,6 +333,7 @@ void pdunshare(struct thread *td);
void pwd_chdir(struct thread *td, struct vnode *vp);
int pwd_chroot(struct thread *td, struct vnode *vp);
int pwd_chroot_chdir(struct thread *td, struct vnode *vp);
void pwd_ensure_dirs(void);
void pwd_set_rootvnode(void);