From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f72.google.com (mail-oo1-f72.google.com [209.85.161.72]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 391EB395D84 for ; Thu, 30 Apr 2026 23:13:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777590813; cv=none; b=g8BY7bxAST7vuNP380BRiTGRRoRuAjIYsChY8RJ1lo/ASrXii6j37DlxavW6TfAZ5TXwC08jYjO8HJPEfqYv0tg3me0Sync561kE8QbdVqa4qXqKutZxnUVdNNErvVlP7GVPtzIsT2yGk3Qu1F9HMSOuYs1iby1qJU/pxe1u9oE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777590813; c=relaxed/simple; bh=rLPBpzQoL509XRjqh7GFxoB0Suy0m8HERukeES775t4=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=FsB4kqyBuHxRZVtDqhpnHwt+iQwDQbJXwi0hDQI21ZChubq9Nm/rGI6p8QCbHqELtEhf7epDvHrxAfPZrueMuknlOrMuL6Gba2W/67ljTBNAWkR7TRC+FOyXkXQ3ZoA+yJ8kQZKP2eN3TUDV2vH5ayWMsqZEXZU/XXLLQ9fX4SA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.161.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oo1-f72.google.com with SMTP id 006d021491bc7-69649771a5aso3231995eaf.2 for ; Thu, 30 Apr 2026 16:13:32 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777590811; x=1778195611; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=wJ60OmNTVUH3YigHFqmed1xVtrqCybKMuMgZj/18FsE=; b=YSgO50k0wjLtoEl9MsWASYLKOknvtq37F65rwRnLF31fh7cwnqPNG2EmqEVUC/02fC xsreLHAVBduIWUevsxSAhBFt5dK1hKDQSb6nFveiPE4hBbR1T+wSsqNSoRNEs75vJWBN XOIY4dR+cNLOqurFZEFmcDydM06wS8Qcle95fq4Oxc8UXdVZgdtqllUMRQhGDypdig1d RLKuNGjGq6L3nX7xMj28x0XAvMTpynoC1OwaJhaibcEE5Um51sqtk2oaYtx5QKjVx2UG UKdfds8QaQhGZIC6a1ztGMItbpdtz8h6oplYtW3aV4KeVpqeWqwccrVWl2QP55LMOp/J /jGg== X-Gm-Message-State: AOJu0YztcsukAJ6Ex/Ry9pcVA/5e3iQmvVoBIvviUEyhJ20h9jFjbZ0y 5X3+IsKS3T2e5OYeXaowihUBLOZah8gkb2aelPjQyYSOKndqccRbP0rbhvl7SOhGQiL8kKVPzl8 FUlJiEkHPAwsUAYxSyOn4FpF6+pyZFPuCiNSGp6eQuiMINSnCaXWXsqLMpZo= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:134b:b0:685:d2b6:6df0 with SMTP id 006d021491bc7-6967a4c4369mr2754592eaf.3.1777590811158; Thu, 30 Apr 2026 16:13:31 -0700 (PDT) Date: Thu, 30 Apr 2026 16:13:31 -0700 In-Reply-To: <00000000000034ae0f05e9f94c79@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69f3e21b.050a0220.312cd3.0008.GAE@google.com> Subject: Forwarded: Re: [syz] KASAN: use-after-free Read in jfs_lazycommit From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: Re: [syz] KASAN: use-after-free Read in jfs_lazycommit Author: tristmd@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master >>From a6c188149cf9056a8692aa45dfd0d429bd07d09f Mon Sep 17 00:00:00 2001 From: Tristan Madani Date: Thu, 30 Apr 2026 23:12:58 +0000 Subject: [PATCH] jfs: drain lazy commit queue during unmount to prevent use-after-free The jfsCommit kernel thread processes committed transactions from TxAnchor.unlock_queue via jfs_lazycommit(). During filesystem unmount, jfs_umount() calls jfs_flush_journal(log, 2) which waits for the log commit queue (log->cqueue) to drain. However, after log I/O completes, lazy transactions are moved to TxAnchor.unlock_queue for asynchronous processing by jfsCommit. If jfs_umount() proceeds to free the jfs_log (via lmLogClose) or jfs_sb_info (via kfree in jfs_put_super) while entries referencing this superblock remain on unlock_queue, the jfsCommit thread will access freed memory when it later processes these entries: - jfs_lazycommit reads sbi->commit_state (UAF of jfs_sb_info) - txLazyCommit accesses JFS_SBI(tblk->sb)->log and takes log->gclock (UAF of jfs_log) Add txLazyDrain() which waits for all entries in TxAnchor.unlock_queue belonging to the unmounting superblock to be processed, and also waits for any in-flight txLazyCommit (IN_LAZYCOMMIT) for this superblock to complete. Call it from both jfs_umount() and jfs_umount_rw() after jfs_flush_journal(). Reported-by: syzbot+c244f4a09ca85dd2ebc1@syzkaller.appspotmail.com Reported-by: syzbot+885a4f3281b8d99c48d8@syzkaller.appspotmail.com Fixes: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Tristan Madani --- fs/jfs/jfs_txnmgr.c | 34 ++++++++++++++++++++++++++++++++++ fs/jfs/jfs_txnmgr.h | 1 + fs/jfs/jfs_umount.c | 8 ++++++++ 3 files changed, 43 insertions(+) diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c index 083dbbb0c3268..e3b2cee416c19 100644 --- a/fs/jfs/jfs_txnmgr.c +++ b/fs/jfs/jfs_txnmgr.c @@ -2791,6 +2791,40 @@ void txLazyUnlock(struct tblock * tblk) LAZY_UNLOCK(flags); } + +/* + * txLazyDrain + * + * Wait for all pending lazy commit entries for this superblock + * to be processed by the jfsCommit thread. Must be called + * before freeing per-filesystem structures during unmount. + */ +void txLazyDrain(struct super_block *sb) +{ + struct jfs_sb_info *sbi = JFS_SBI(sb); + struct tblock *tblk; + unsigned long flags; + bool found; + + do { + found = false; + LAZY_LOCK(flags); + list_for_each_entry(tblk, &TxAnchor.unlock_queue, cqueue) { + if (tblk->sb == sb) { + found = true; + break; + } + } + if (!found && (sbi->commit_state & IN_LAZYCOMMIT)) + found = true; + LAZY_UNLOCK(flags); + + if (found) { + wake_up(&jfs_commit_thread_wait); + schedule_timeout_uninterruptible(1); + } + } while (found); +} static void LogSyncRelease(struct metapage * mp) { struct jfs_log *log = mp->log; diff --git a/fs/jfs/jfs_txnmgr.h b/fs/jfs/jfs_txnmgr.h index ba71eb5ced567..fbbaed26c52bd 100644 --- a/fs/jfs/jfs_txnmgr.h +++ b/fs/jfs/jfs_txnmgr.h @@ -291,6 +291,7 @@ extern void txFreelock(struct inode *); extern int lmLog(struct jfs_log *, struct tblock *, struct lrd *, struct tlock *); extern void txQuiesce(struct super_block *); +extern void txLazyDrain(struct super_block *); extern void txResume(struct super_block *); extern void txLazyUnlock(struct tblock *); extern int jfs_lazycommit(void *); diff --git a/fs/jfs/jfs_umount.c b/fs/jfs/jfs_umount.c index 18569f1eaabdb..657707361be2a 100644 --- a/fs/jfs/jfs_umount.c +++ b/fs/jfs/jfs_umount.c @@ -58,6 +58,13 @@ int jfs_umount(struct super_block *sb) */ jfs_flush_journal(log, 2); + /* + * Drain any pending lazy commit entries for this filesystem so + * the jfsCommit thread does not access freed structures. + */ + if (log) + txLazyDrain(sb); + /* * Hold log lock so write_special_inodes (lmLogSync) cannot see * this sbi with a NULL inode pointer while iterating log->sb_list. @@ -142,6 +149,7 @@ int jfs_umount_rw(struct super_block *sb) * remove file system from log active file system list. */ jfs_flush_journal(log, 2); + txLazyDrain(sb); /* * Make sure all metadata makes it to disk -- 2.47.3