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Allow absolute paths for O_BENEATH.

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The path must have a tail which does not escape starting/topping
directory.  The documentation will come shortly, see the man pages
commit message for the reason of separate commit.

Reviewed by:	jilles (previous version)
Discussed with:	emaste
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D17714
This commit is contained in:
Konstantin Belousov 2018-11-11 00:04:36 +00:00
parent 71ec454d66
commit ade85c5eec
2 changed files with 54 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
sys/kern/vfs_lookup.c
View File

@ -177,6 +177,13 @@ nameicap_tracker_add(struct nameidata *ndp, struct vnode *dp)
if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp->v_type != VDIR)
return;
if ((ndp->ni_lcf & (NI_LCF_BENEATH_ABS | NI_LCF_BENEATH_LATCHED)) ==
NI_LCF_BENEATH_ABS) {
MPASS((ndp->ni_lcf & NI_LCF_LATCH) != 0);
if (dp != ndp->ni_beneath_latch)
return;
ndp->ni_lcf |= NI_LCF_BENEATH_LATCHED;
}
nt = uma_zalloc(nt_zone, M_WAITOK);
vhold(dp);
nt->dp = dp;
@ -184,7 +191,7 @@ nameicap_tracker_add(struct nameidata *ndp, struct vnode *dp)
}
static void
nameicap_cleanup(struct nameidata *ndp)
nameicap_cleanup(struct nameidata *ndp, bool clean_latch)
{
struct nameicap_tracker *nt, *nt1;
@ -195,6 +202,8 @@ nameicap_cleanup(struct nameidata *ndp)
vdrop(nt->dp);
uma_zfree(nt_zone, nt);
}
if (clean_latch && (ndp->ni_lcf & NI_LCF_LATCH) != 0)
vrele(ndp->ni_beneath_latch);
}
/*
@ -222,6 +231,11 @@ nameicap_check_dotdot(struct nameidata *ndp, struct vnode *dp)
if (dp == nt->dp)
return (0);
}
if ((ndp->ni_lcf & NI_LCF_BENEATH_ABS) != 0) {
ndp->ni_lcf &= ~NI_LCF_BENEATH_LATCHED;
nameicap_cleanup(ndp, false);
return (0);
}
return (ENOTCAPABLE);
}
@ -242,14 +256,18 @@ namei_handle_root(struct nameidata *ndp, struct vnode **dpp)
struct componentname *cnp;
cnp = &ndp->ni_cnd;
if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 ||
(cnp->cn_flags & BENEATH) != 0) {
if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0) {
#ifdef KTRACE
if (KTRPOINT(curthread, KTR_CAPFAIL))
ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
#endif
return (ENOTCAPABLE);
}
if ((cnp->cn_flags & BENEATH) != 0) {
ndp->ni_lcf |= NI_LCF_BENEATH_ABS;
ndp->ni_lcf &= ~NI_LCF_BENEATH_LATCHED;
nameicap_cleanup(ndp, false);
}
while (*(cnp->cn_nameptr) == '/') {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
@ -290,6 +308,7 @@ namei(struct nameidata *ndp)
struct thread *td;
struct proc *p;
cap_rights_t rights;
struct filecaps dirfd_caps;
struct uio auio;
int error, linklen, startdir_used;
@ -427,6 +446,23 @@ namei(struct nameidata *ndp)
if (error == 0 && dp->v_type != VDIR)
error = ENOTDIR;
}
if (error == 0 && (ndp->ni_lcf & NI_LCF_BENEATH_ABS) != 0) {
if (ndp->ni_dirfd == AT_FDCWD) {
ndp->ni_beneath_latch = fdp->fd_cdir;
vrefact(ndp->ni_beneath_latch);
} else {
rights = ndp->ni_rightsneeded;
cap_rights_set(&rights, CAP_LOOKUP);
error = fgetvp_rights(td, ndp->ni_dirfd, &rights,
&dirfd_caps, &ndp->ni_beneath_latch);
if (error == 0 && dp->v_type != VDIR) {
vrele(ndp->ni_beneath_latch);
error = ENOTDIR;
}
}
if (error == 0)
ndp->ni_lcf |= NI_LCF_LATCH;
}
FILEDESC_SUNLOCK(fdp);
if (ndp->ni_startdir != NULL && !startdir_used)
vrele(ndp->ni_startdir);
@ -456,9 +492,15 @@ namei(struct nameidata *ndp)
namei_cleanup_cnp(cnp);
} else
cnp->cn_flags |= HASBUF;
nameicap_cleanup(ndp);
SDT_PROBE2(vfs, namei, lookup, return, 0, ndp->ni_vp);
return (0);
if ((ndp->ni_lcf & (NI_LCF_BENEATH_ABS |
NI_LCF_BENEATH_LATCHED)) == NI_LCF_BENEATH_ABS) {
NDFREE(ndp, 0);
error = ENOTCAPABLE;
}
nameicap_cleanup(ndp, true);
SDT_PROBE2(vfs, namei, lookup, return, error,
(error == 0 ? ndp->ni_vp : NULL));
return (error);
}
if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
error = ELOOP;
@ -529,8 +571,9 @@ namei(struct nameidata *ndp)
vrele(ndp->ni_dvp);
out:
vrele(ndp->ni_rootdir);
MPASS(error != 0);
namei_cleanup_cnp(cnp);
nameicap_cleanup(ndp);
nameicap_cleanup(ndp, true);
SDT_PROBE2(vfs, namei, lookup, return, error, NULL);
return (error);
}

4
sys/sys/namei.h
View File

@ -100,6 +100,7 @@ struct nameidata {
*/
struct componentname ni_cnd;
struct nameicap_tracker_head ni_cap_tracker;
struct vnode *ni_beneath_latch;
};
#ifdef _KERNEL
@ -163,6 +164,9 @@ struct nameidata {
*/
#define NI_LCF_STRICTRELATIVE 0x0001 /* relative lookup only */
#define NI_LCF_CAP_DOTDOT 0x0002 /* ".." in strictrelative case */
#define NI_LCF_BENEATH_ABS 0x0004 /* BENEATH with absolute path */
#define NI_LCF_BENEATH_LATCHED 0x0008 /* BENEATH_ABS traversed starting dir */
#define NI_LCF_LATCH 0x0010 /* ni_beneath_latch valid */
/*
* Initialization of a nameidata structure.