From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E34584F5E04 for ; Wed, 14 Oct 2026 11:23:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.132 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791977009; cv=none; b=vC/DDtQ3eKkNfTeKTcENzRuT0TQEHtsLUQmw8ajKh0pGvaNvPx5tAiBSiiGE9aXwMg+YJ97Zcyx7ZEuQmA7DY6L2l4DsxmINMf9BrM8YRPQkui4Q7A5PCekw+YvqSnyMSfVCRW3BYNcXh9GM0WfjpT4ZxQNiMqD3OGffrBioZFo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791977009; c=relaxed/simple; bh=gvZblxMbNnPBwlfPk4lfkDR4K+EEAEYN0ydugwx77/s=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=OFRo0JecPcwpSEi35o0/J9u1Vj+xlMfjlvmf46q+Q5H6PbzZsIN06eXwmRZsYeMCRKAsXjjNUOJT6OBzFI74p2BEx1GqAfunuH9gld2BJHYDqVfY9YUbMPE2jOuVUyPXplfEp4bNAslSwm9epkNMgACvPaH71UVhvc80H1xbvcA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=SkHe+nrx; arc=none smtp.client-ip=115.124.30.132 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="SkHe+nrx" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1791977002; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=caGDUFxt5LVNaqNJ4efKRsvklAhDC/F8AjH3Q+78AlA=; b=SkHe+nrxrBZW5758aA9sh8rA63Kj/jyPMmRcrN7sJT6cO5vkMj8hhK/ZfJIUdQb0246mtQLwk+g98Eg4tPyw3zpxnlHMbUdyzhCxbopaywzMA84K30GbVejIcTbzVkXnxT0u4aEZSsNZD1Okd8kI+Go4KPDJU3lsugfkJvEEbF4= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045098064;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0XCoySAW_1791977001; Received: from localhost(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0XCoySAW_1791977001 cluster:ay36) by smtp.aliyun-inc.com; Wed, 14 Oct 2026 19:23:21 +0800 From: Joseph Qi To: Andrew Morton , Heming Zhao Cc: Mark Fasheh , Joel Becker , ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH] ocfs2/dlm: hold the lookup reference across convert AST enqueue Date: Wed, 14 Oct 2026 19:23:21 +0800 Message-Id: <20261014112321.2955584-1-joseph.qi@linux.alibaba.com> X-Mailer: git-send-email 2.39.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit dlm_convert_lock_handler() drops the reference it took when it found the lock on res->granted at its leave label, one statement before it calls dlm_queue_ast(). dlm_free_dead_locks() takes res->spinlock and drops the list and base references, so a peer death landing in that gap leaves the handler's own put as the one that frees the lock, and __dlm_queue_ast() then reads lock->lockres from freed memory. The handler is registered next to dlm_create_lock_handler(), so a convert message buffered on a dying peer's socket arrives on the same o2net receive work that o2net_disconnect_node() does not wait for. The two can interleave as follows, with the reference counts as they are before this fix: Socket data-ready Node-down thread Receive worker ----------------- ---------------- -------------- o2net_data_ready() select sc under callback read lock o2net_disconnect_node() queue shutdown begin flush; new color queue sc_rx_work in the new color release callback lock shutdown socket flush returns read buffered convert_lock dlm_convert_lock_handler() find lock on res->granted dlm_lock_get() refs = 3 lock res->spinlock __dlmconvert_master() call_ast = 1 unlock res->spinlock DLM node-down cleanup lock res->spinlock dlm_free_dead_locks() unlink lock put list ref refs = 2 put base ref refs = 1 unlock res->spinlock dlm_lock_put() refs = 0 free lock dlm_queue_ast() __dlm_queue_ast() read lock->lockres (use-after-free) __dlmconvert_master() only moves the lock between lists, so the count entering the gap is base, list and lookup. Drop the lookup reference after the AST is queued instead of before it and the race ends with the one __dlm_queue_ast() took, which dlm_flush_asts() releases later with ast_pending cleared and ast_list unlinked. No extra get is needed, and the normal case ends with the same count as before. dlmconvert_master() has the same shape but is only reached from dlmlock() for a lock this node owns, which dlm_free_dead_locks() never matches. Fixes: 2c5c54aca9d0 ("ocfs2/dlm: Add missing dlm_lock_put()s") Cc: Signed-off-by: Joseph Qi --- fs/ocfs2/dlm/dlmconvert.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/ocfs2/dlm/dlmconvert.c b/fs/ocfs2/dlm/dlmconvert.c index 450d46eefab32..8a828448ba958 100644 --- a/fs/ocfs2/dlm/dlmconvert.c +++ b/fs/ocfs2/dlm/dlmconvert.c @@ -534,15 +534,19 @@ int dlm_convert_lock_handler(struct o2net_msg *msg, u32 len, void *data, } leave: - if (lock) - dlm_lock_put(lock); - /* either queue the ast or release it, if reserved */ if (call_ast) dlm_queue_ast(dlm, lock); else if (ast_reserved) dlm_lockres_release_ast(dlm, res); + /* + * Keep the lock alive through AST enqueue: a concurrent + * dlm_free_dead_locks() drops the list and base references. + */ + if (lock) + dlm_lock_put(lock); + if (kick_thread) dlm_kick_thread(dlm, res); -- 2.39.3