git: 6a3047840dfb - stable/13 - cache: handle NOFOLLOW requests for symlinks

[Mateusz Guzik]

The branch stable/13 has been updated by mjg:

URL: https://cgit.FreeBSD.org/src/commit/?id=6a3047840dfbbdb59d96a325f295f42755648545

commit 6a3047840dfbbdb59d96a325f295f42755648545
Author:     Mateusz Guzik <mjg at FreeBSD.org>
AuthorDate: 2021-01-26 22:14:49 +0000
Commit:     Mateusz Guzik <mjg at FreeBSD.org>
CommitDate: 2021-02-01 12:39:18 +0000

    cache: handle NOFOLLOW requests for symlinks
    
    Tested by:      pho
    
    (cherry picked from commit 8cbd164a179c182e8fd4a71f366bc48fe840eafb)
---
 sys/kern/vfs_cache.c | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index ff8aad14001b..b8b876657211 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -4307,11 +4307,22 @@ cache_fplookup_final_modifying(struct cache_fpl *fpl)
 	}
 
 	/*
-	 * Check if the target is either a symlink or a mount point.
-	 * Since we expect this to be the terminal vnode it should
-	 * almost never be true.
+	 * If they want the symlink itself we are fine, but if they want to
+	 * follow it regular lookup has to be engaged.
 	 */
-	if (__predict_false(tvp->v_type == VLNK || cache_fplookup_is_mp(fpl))) {
+	if (tvp->v_type == VLNK) {
+		if ((cnp->cn_flags & FOLLOW) != 0) {
+			vput(dvp);
+			vput(tvp);
+			return (cache_fpl_aborted(fpl));
+		}
+	}
+
+	/*
+	 * Since we expect this to be the terminal vnode it should almost never
+	 * be a mount point.
+	 */
+	if (__predict_false(cache_fplookup_is_mp(fpl))) {
 		vput(dvp);
 		vput(tvp);
 		return (cache_fpl_aborted(fpl));
@@ -4614,7 +4625,15 @@ cache_fplookup_noentry(struct cache_fpl *fpl)
 		return (cache_fpl_handled(fpl));
 	}
 
-	if (__predict_false(tvp->v_type == VLNK || cache_fplookup_is_mp(fpl))) {
+	if (tvp->v_type == VLNK) {
+		if ((cnp->cn_flags & FOLLOW) != 0) {
+			vput(dvp);
+			vput(tvp);
+			return (cache_fpl_aborted(fpl));
+		}
+	}
+
+	if (__predict_false(cache_fplookup_is_mp(fpl))) {
 		vput(dvp);
 		vput(tvp);
 		return (cache_fpl_aborted(fpl));