git: cea7c564c70a - main - namei: Reset the lookup to start from the real root for abs symlink target

The branch main has been updated by dchagin:

URL: https://cgit.FreeBSD.org/src/commit/?id=cea7c564c70aa660d833e9a571aaca4119c0b714

commit cea7c564c70aa660d833e9a571aaca4119c0b714
Author:     Dmitry Chagin <dchagin@FreeBSD.org>
AuthorDate: 2023-06-13 12:24:25 +0000
Commit:     Dmitry Chagin <dchagin@FreeBSD.org>
CommitDate: 2023-06-13 12:24:25 +0000

    namei: Reset the lookup to start from the real root for abs symlink target
    
    Since fd745e1d Linux ABI specifies alternative root directory to reroot
    lookups. First, an attempt is made to lookup the file in /ABI/original-path.
    If that fails, the lookup is done in /original-path. In case of lookup
    symbolic link with leading / in target namei() fails due to reroot reloads
    original file name.
    To avoid this handle restart in a special maner, without origin path name
    reloading.
    
    Reported by:            Goran Mekić, Vincent Milum Jr
    Tested by:              Goran Mekić
    Reviewed by:            kib
    Differential Revision:  https://reviews.freebsd.org/D40479
---
 sys/kern/vfs_lookup.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
index 20919fb38b4d..dd6282a45d97 100644
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -721,6 +721,14 @@ restart:
 		 */
 		cnp->cn_nameptr = cnp->cn_pnbuf;
 		if (*(cnp->cn_nameptr) == '/') {
+			/*
+			 * Reset the lookup to start from the real root without
+			 * origin path name reloading.
+			 */
+			if (__predict_false(ndp->ni_rootdir != pwd->pwd_rdir)) {
+				cnp->cn_flags |= ISRESTARTED;
+				ndp->ni_rootdir = pwd->pwd_rdir;
+			}
 			vrele(dp);
 			error = namei_handle_root(ndp, &dp);
 			if (error != 0)