linux-kernel - Re: [syzbot] Re: [syzbot] [f2fs?] KASAN: null-ptr-deref Write in f2fs_stop_gc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <000000000000b14c3e061e0de63d@google.com>
Date: Thu, 25 Jul 2024 01:08:34 -0700
From: syzbot <syzbot+1a8e2b31f2ac9bd3d148@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org
Subject: Re: [syzbot] Re: [syzbot] [f2fs?] KASAN: null-ptr-deref Write in f2fs_stop_gc_thread

For archival purposes, forwarding an incoming command email to
linux-kernel@...r.kernel.org.

***

Subject: Re: [syzbot] [f2fs?] KASAN: null-ptr-deref Write in f2fs_stop_gc_thread
Author: lizhi.xu@...driver.com

before thread stop and free gc_thread, set sbi->gc_thread to NULL, 
and add lock for reentry f2fs_stop_gc_thread.

#syz test: upstream 2c9b3512402e

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 6066c6eecf41..228cad05b32b 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -203,14 +203,20 @@ int f2fs_start_gc_thread(struct f2fs_sb_info *sbi)
 
 void f2fs_stop_gc_thread(struct f2fs_sb_info *sbi)
 {
-	struct f2fs_gc_kthread *gc_th = sbi->gc_thread;
+	struct f2fs_gc_kthread *gc_th;
+	static DEFINE_MUTEX(gct_mutex);
 
+	mutex_lock(&gct_mutex);
+	gc_th = sbi->gc_thread;
 	if (!gc_th)
-		return;
+		goto unlock;
+
 	kthread_stop(gc_th->f2fs_gc_task);
 	wake_up_all(&gc_th->fggc_wq);
-	kfree(gc_th);
 	sbi->gc_thread = NULL;
+	kfree(gc_th);
+unlock:
+	mutex_unlock(&gct_mutex);
 }
 
 static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)