From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 10C2031B117; Mon, 18 Aug 2025 13:12:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755522769; cv=none; b=JQci+pPjSq00mQfxY170UgtTpRQaxHn0SU7HFyqJzWGDbO22D9RIhNwyphaP5cTFKHMsiltxWArBxOipB1dOLiH4CHy8gh6sARYjlmT/FraCqvC4t3OFS7pXmU6YEX0Uigu2zdv2aK1Bw1S0VV51jUa31GqfyFjoYUMZau9WJ5U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755522769; c=relaxed/simple; bh=e5emeFhhz5DbXP69MwjMtv9ZRPoLwbLRuEh5cUAAZ8Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uv8F2t7zE3hk8eZ+jnJ+B5Aqec/swtpdf861e9DMNecla0wXzKkjspjwWqTkid+D6+HLALGJYc3ODR8xYYXqiV2KgN0OsmIy073VfwlVUW7ZFCV/UHp1hemIqzMYkM0TaHyGkp4dkTjGDqcNyrWuDfc2Pr0ZyBnP/1DkNagiVzE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kRTc447C; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="kRTc447C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 516F8C4CEEB; Mon, 18 Aug 2025 13:12:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755522768; bh=e5emeFhhz5DbXP69MwjMtv9ZRPoLwbLRuEh5cUAAZ8Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kRTc447C1K1Ii4/RdxaRgJyX/Mg8bbqxQJFT59QkfcmQawB5jH4N8F9yiG0VgfttF xmoGwco+Q1/V1OLI3zZLio6fXOj57r52LksvxyB1BHIa+WJPnY72fPDYDX8mr6Cgrm RQXuGa1Alr2MFi/VKb0dFNfNPk8X7k4YofT59ZE8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Breno Leitao , Jakub Kicinski , Catalin Marinas , Andrew Morton Subject: [PATCH 6.12 415/444] mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock Date: Mon, 18 Aug 2025 14:47:21 +0200 Message-ID: <20250818124504.488781199@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250818124448.879659024@linuxfoundation.org> References: <20250818124448.879659024@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Breno Leitao commit 47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2 upstream. When netpoll is enabled, calling pr_warn_once() while holding kmemleak_lock in mem_pool_alloc() can cause a deadlock due to lock inversion with the netconsole subsystem. This occurs because pr_warn_once() may trigger netpoll, which eventually leads to __alloc_skb() and back into kmemleak code, attempting to reacquire kmemleak_lock. This is the path for the deadlock. mem_pool_alloc() -> raw_spin_lock_irqsave(&kmemleak_lock, flags); -> pr_warn_once() -> netconsole subsystem -> netpoll -> __alloc_skb -> __create_object -> raw_spin_lock_irqsave(&kmemleak_lock, flags); Fix this by setting a flag and issuing the pr_warn_once() after kmemleak_lock is released. Link: https://lkml.kernel.org/r/20250731-kmemleak_lock-v1-1-728fd470198f@debian.org Fixes: c5665868183f ("mm: kmemleak: use the memory pool for early allocations") Signed-off-by: Breno Leitao Reported-by: Jakub Kicinski Acked-by: Catalin Marinas Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/kmemleak.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -465,6 +465,7 @@ static struct kmemleak_object *mem_pool_ { unsigned long flags; struct kmemleak_object *object; + bool warn = false; /* try the slab allocator first */ if (object_cache) { @@ -483,8 +484,10 @@ static struct kmemleak_object *mem_pool_ else if (mem_pool_free_count) object = &mem_pool[--mem_pool_free_count]; else - pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); + warn = true; raw_spin_unlock_irqrestore(&kmemleak_lock, flags); + if (warn) + pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); return object; }