git: 6d9339c7b1b6 - stable/14 - inotify: Work around the vput() bug directly

The branch stable/14 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=6d9339c7b1b60b97ea1e9391af31b7f4e8de0d00

commit 6d9339c7b1b60b97ea1e9391af31b7f4e8de0d00
Author:     Mark Johnston <[email protected]>
AuthorDate: 2025-11-15 18:00:44 +0000
Commit:     Mark Johnston <[email protected]>
CommitDate: 2026-08-05 15:15:16 +0000

    inotify: Work around the vput() bug directly
    
    For 15.0, apply a minimal fix which at least ensures that inotify can't
    trigger the latent race described in commit 99cb3dca4773 ("vnode: Rework
    vput() to avoid holding the vnode lock after decrementing").
    
    Reviewed by:    olce, kib
    MFC after:      3 days
    Differential Revision:  https://reviews.freebsd.org/D53774
    
    (cherry picked from commit ebc17879f0885ca87644980f6275b9759b311eb3)
---
 sys/kern/vfs_inotify.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/sys/kern/vfs_inotify.c b/sys/kern/vfs_inotify.c
index eba2f0147409..6b82d5e9ab96 100644
--- a/sys/kern/vfs_inotify.c
+++ b/sys/kern/vfs_inotify.c
@@ -377,7 +377,14 @@ inotify_unlink_watch_locked(struct inotify_softc *sc, struct inotify_watch *watc
 static void
 inotify_free_watch(struct inotify_watch *watch)
 {
-	vrele(watch->vp);
+	/*
+	 * Formally, we don't need to lock the vnode here.  However, if we
+	 * don't, and vrele() releases the last reference, it's possible the
+	 * vnode will be recycled while a different thread holds the vnode lock.
+	 * Work around this bug by acquiring the lock here.
+	 */
+	(void)vn_lock(watch->vp, LK_EXCLUSIVE | LK_RETRY);
+	vput(watch->vp);
 	free(watch, M_INOTIFY);
 }