git: a718431c30a5 - main - lookup(): ensure that openat("/", "..", O_RESOLVE_BENEATH) fails

[Konstantin Belousov]

The branch main has been updated by kib:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=a718431c30a57226bc7c1a9181fc84bab00641a1

commit a718431c30a57226bc7c1a9181fc84bab00641a1
Author:     Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2023-04-23 23:21:42 +0000
Commit:     Konstantin Belousov <k...@freebsd.org>
CommitDate: 2023-04-24 21:32:10 +0000

    lookup(): ensure that openat("/", "..", O_RESOLVE_BENEATH) fails
    
    PR:     269780
    Reported by:    Dan Gohman <dev@sunfishcode.online>
    Reviewed by:    emaste, markj
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D39773
---
 sys/kern/vfs_lookup.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
index d9a9cabde177..66a8b267f346 100644
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -1083,12 +1083,16 @@ dirloop:
                             pr = pr->pr_parent)
                                if (dp == pr->pr_root)
                                        break;
-                       if (dp == ndp->ni_rootdir || 
-                           dp == ndp->ni_topdir || 
-                           dp == rootvnode ||
-                           pr != NULL ||
-                           ((dp->v_vflag & VV_ROOT) != 0 &&
-                            (cnp->cn_flags & NOCROSSMOUNT) != 0)) {
+                       bool isroot = dp == ndp->ni_rootdir ||
+                           dp == ndp->ni_topdir || dp == rootvnode ||
+                           pr != NULL;
+                       if (isroot && (ndp->ni_lcf &
+                           NI_LCF_STRICTRELATIVE) != 0) {
+                               error = ENOTCAPABLE;
+                               goto capdotdot;
+                       }
+                       if (isroot || ((dp->v_vflag & VV_ROOT) != 0 &&
+                           (cnp->cn_flags & NOCROSSMOUNT) != 0)) {
                                ndp->ni_dvp = dp;
                                ndp->ni_vp = dp;
                                VREF(dp);
@@ -1109,6 +1113,7 @@ dirloop:
                            LK_RETRY, ISDOTDOT));
                        error = nameicap_check_dotdot(ndp, dp);
                        if (error != 0) {
+capdotdot:
 #ifdef KTRACE
                                if (KTRPOINT(curthread, KTR_CAPFAIL))
                                        ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);