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 113223EFD09 for ; Fri, 8 May 2026 14:24:09 +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=1778250249; cv=none; b=E0cZOxF2MXzZ9zOQoSnOwEsJ81ZdAi5uClihG90mSL6mzlNqS4Z6vBnA+v27x9ot57VLNO5suOa7roAKq5ZKLMr8gAPhc7BiTKKMPEibLUQVSTHrhOUzZRtTjvU2rUkbv5XvreqZLy0WUl7aORSxSzkhZV1Ij76DEUEtSPOC4xo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778250249; c=relaxed/simple; bh=67XbIuQgQWnY+yUGoa2uX7Vo+qLh0Le1t6moC39viUY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=iR/cEio2tSGgxJXrAKe+gtXkMN6Zz5C1I7x5fFyGQ667VXGg0ajHHvCrqDu/QBIQCW1P/Um4jUCtIRurlHlyCXHn72zrw4khU+KOmNSiKKVFjbeNfmSpSU5ZNLhfeRCKIkuYQWXYu9qhyL3L4uCQOKgECyADtMqp6EYgBEYI7uI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JBERb4To; 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="JBERb4To" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96B37C2BCC9; Fri, 8 May 2026 14:24:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778250249; bh=67XbIuQgQWnY+yUGoa2uX7Vo+qLh0Le1t6moC39viUY=; h=From:To:Cc:Subject:Date:Reply-To:From; b=JBERb4ToanzXxrs7SYiEBeg1MZvDCvK0g5A9VnxIyF0YRGybFOybHYGy++KL10Ddp 3g4saktiQVwsxIzLJ49iO5e5iScceeliRRZyFY/TbRAdTFMhyzIY+WcQU2CEUUfRw5 NEwpbnGUOhwDRzVKNPxxGUirgkTbg8DucsjI9n0Q= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-43385: net: Fix rcu_tasks stall in threaded busypoll Date: Fri, 8 May 2026 16:21:54 +0200 Message-ID: <2026050834-CVE-2026-43385-057b@gregkh> X-Mailer: git-send-email 2.54.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3571; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=w7K+F2kNIt25+nzDBX/KQU/d8rpjtTfxCFm/Js95Wik=; b=owGbwMvMwCRo6H6F97bub03G02pJDJl/P+ZdMT6bObMwaxrXLNdjvxplb7M2b+S1OvjcojDhZ qPtrRLpjlgWBkEmBlkxRZYv23iO7q84pOhlaHsaZg4rE8gQBi5OAZiIVijDfKeLQZG57AG61S19 E+8fiC7d1MY4jWF+5tb/zbbirjvrsyd9Ewu1a9+9YIonAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: net: Fix rcu_tasks stall in threaded busypoll I was debugging a NIC driver when I noticed that when I enable threaded busypoll, bpftrace hangs when starting up. dmesg showed: rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 10658 jiffies old. rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 40793 jiffies old. rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 131273 jiffies old. rcu_tasks_wait_gp: rcu_tasks grace period number 85 (since boot) is 402058 jiffies old. INFO: rcu_tasks detected stalls on tasks: 00000000769f52cd: .N nvcsw: 2/2 holdout: 1 idle_cpu: -1/64 task:napi/eth2-8265 state:R running task stack:0 pid:48300 tgid:48300 ppid:2 task_flags:0x208040 flags:0x00004000 Call Trace: ? napi_threaded_poll_loop+0x27c/0x2c0 ? __pfx_napi_threaded_poll+0x10/0x10 ? napi_threaded_poll+0x26/0x80 ? kthread+0xfa/0x240 ? __pfx_kthread+0x10/0x10 ? ret_from_fork+0x31/0x50 ? __pfx_kthread+0x10/0x10 ? ret_from_fork_asm+0x1a/0x30 The cause is that in threaded busypoll, the main loop is in napi_threaded_poll rather than napi_threaded_poll_loop, where the latter rarely iterates more than once within its loop. For rcu_softirq_qs_periodic inside napi_threaded_poll_loop to report its qs state, the last_qs must be 100ms behind, and this can't happen because napi_threaded_poll_loop rarely iterates in threaded busypoll, and each time napi_threaded_poll_loop is called last_qs is reset to latest jiffies. This patch changes so that in threaded busypoll, last_qs is saved in the outer napi_threaded_poll, and whether busy_poll_last_qs is NULL indicates whether napi_threaded_poll_loop is called for busypoll. This way last_qs would not reset to latest jiffies on each invocation of napi_threaded_poll_loop. The Linux kernel CVE team has assigned CVE-2026-43385 to this issue. Affected and fixed versions =========================== Issue introduced in 6.19 with commit c18d4b190a46651726c9a952667c74d2deb33c28 and fixed in 6.19.9 with commit 52459201d0df3fdbb1d281738b7b772e2cacb49c Issue introduced in 6.19 with commit c18d4b190a46651726c9a952667c74d2deb33c28 and fixed in 7.0 with commit 1a86a1f7d88996085934139fa4c063b6299a2dd3 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-43385 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: net/core/dev.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/52459201d0df3fdbb1d281738b7b772e2cacb49c https://git.kernel.org/stable/c/1a86a1f7d88996085934139fa4c063b6299a2dd3