Merge tag 'v6.6-rc7.vfs.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs fix from Christian Brauner:
 "An openat() call from io_uring triggering an audit call can apparently
  cause the refcount of struct filename to be incremented from multiple
  threads concurrently during async execution, triggering a refcount
  underflow and hitting a BUG_ON(). That bug has been lurking around
  since at least v5.16 apparently.

  Switch to an atomic counter to fix that. The underflow check is
  downgraded from a BUG_ON() to a WARN_ON_ONCE() but we could easily
  remove that check altogether tbh"

* tag 'v6.6-rc7.vfs.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  audit,io_uring: io_uring openat triggers audit reference count underflow

1 files changed, 4 insertions, 4 deletions

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 21d2fa815e78..6f0d6fb6523f 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2212,7 +2212,7 @@ __audit_reusename(const __user char *uptr)
 		if (!n->name)
 			continue;
 		if (n->name->uptr == uptr) {
-			n->name->refcnt++;
+			atomic_inc(&n->name->refcnt);
 			return n->name;
 		}
 	}
@@ -2241,7 +2241,7 @@ void __audit_getname(struct filename *name)
 	n->name = name;
 	n->name_len = AUDIT_NAME_FULL;
 	name->aname = n;
-	name->refcnt++;
+	atomic_inc(&name->refcnt);
 }
 
 static inline int audit_copy_fcaps(struct audit_names *name,
@@ -2373,7 +2373,7 @@ out_alloc:
 		return;
 	if (name) {
 		n->name = name;
-		name->refcnt++;
+		atomic_inc(&name->refcnt);
 	}
 
 out:
@@ -2500,7 +2500,7 @@ void __audit_inode_child(struct inode *parent,
 		if (found_parent) {
 			found_child->name = found_parent->name;
 			found_child->name_len = AUDIT_NAME_FULL;
-			found_child->name->refcnt++;
+			atomic_inc(&found_child->name->refcnt);
 		}
 	}