git: 7c1e4aab7934 - main - vfs_hash_insert: ensure that predicate is true

[Konstantin Belousov]

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=7c1e4aab7934933f0669c2b922976b30ed628a3f

commit 7c1e4aab7934933f0669c2b922976b30ed628a3f
Author:     Konstantin Belousov <kib at FreeBSD.org>
AuthorDate: 2021-08-17 13:47:25 +0000
Commit:     Konstantin Belousov <kib at FreeBSD.org>
CommitDate: 2021-08-27 15:39:45 +0000

    vfs_hash_insert: ensure that predicate is true
    
    After vnode lock, recheck v_hash. When vfs_hash_insert() is used with
    a predicate, recheck it after the selected vnode is locked. Since
    vfs_hash_lock is dropped, vnode could be rehashed during the sleep for
    the vnode lock, which could go unnoticed there.
    
    Reported and tested by: pho
    Reviewed by:    mckusick, rmacklem
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D31464
---
 sys/kern/vfs_hash.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sys/kern/vfs_hash.c b/sys/kern/vfs_hash.c
index e10e9b57e316..c5d67c8b2b33 100644
--- a/sys/kern/vfs_hash.c
+++ b/sys/kern/vfs_hash.c
@@ -93,8 +93,14 @@ vfs_hash_get(const struct mount *mp, u_int hash, int flags, struct thread *td,
 			error = vget_finish(vp, flags, vs);
 			if (error == ENOENT && (flags & LK_NOWAIT) == 0)
 				break;
-			if (error)
+			if (error != 0)
 				return (error);
+			if (vp->v_hash != hash ||
+			    (fn != NULL && fn(vp, arg))) {
+				vput(vp);
+				/* Restart the bucket walk. */
+				break;
+			}
 			*vpp = vp;
 			return (0);
 		}