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 1A34B2C9D; Mon, 23 Jun 2025 21:21:17 +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=1750713679; cv=none; b=avaRIdA4UJmj/nX0KDMVajCDfSvuImiCa3nIxei+ZQkSNaA4DiHtVV38SPK4kOUA3cZM0i1oANgmwdXAnNaQa4VTUk6YGC743nNFb7s9EKMjhoZUskARV2AiojVT+TydNFiEQjev9D/1+6qtRjm31ggKWOdifuMAm6VBqXdZDFg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750713679; c=relaxed/simple; bh=JyJKooyiatvjPRSEOVTDOOVxtNCkpFj9YVZ3Ym2Bs/s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UKfcl4VnVUYni5al3pQ2vdOBUDQY+0M8phmGpKZGQv6lNHl6Q3itCZsP3DnJ6wBQvzYfOSnVGn8c8AqNI6VVUTOwic5Kagj1Nx5qRrs+BRFqewTv8zeeEX+IxFPIdLRukJjg9SrOcphronLybdRISA7bh0c+Bl22Zt/wWoS5+W0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zxCSzTwS; 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="zxCSzTwS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65550C4CEEA; Mon, 23 Jun 2025 21:21:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750713677; bh=JyJKooyiatvjPRSEOVTDOOVxtNCkpFj9YVZ3Ym2Bs/s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zxCSzTwS+3MTDK2aa6I4x7mrNgR7E+gV+ds5djJV1t58s/80tkkgmj44P2vxC+9+y aBFowJ+yYF9RT3dEb2px0vUv6ZfyORP8Oe+QAY646bVDFM7q4NrkFmhnwB3Owu9a3P oKaANEInD1aadzX/icgU/ioJc8KQj7vfpjhWIX8o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jeongjun Park , Richard Cochran , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 140/411] ptp: remove ptp->n_vclocks check logic in ptp_vclock_in_use() Date: Mon, 23 Jun 2025 15:04:44 +0200 Message-ID: <20250623130637.121569450@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130632.993849527@linuxfoundation.org> References: <20250623130632.993849527@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jeongjun Park [ Upstream commit 87f7ce260a3c838b49e1dc1ceedf1006795157a2 ] There is no disagreement that we should check both ptp->is_virtual_clock and ptp->n_vclocks to check if the ptp virtual clock is in use. However, when we acquire ptp->n_vclocks_mux to read ptp->n_vclocks in ptp_vclock_in_use(), we observe a recursive lock in the call trace starting from n_vclocks_store(). ============================================ WARNING: possible recursive locking detected 6.15.0-rc6 #1 Not tainted -------------------------------------------- syz.0.1540/13807 is trying to acquire lock: ffff888035a24868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_vclock_in_use drivers/ptp/ptp_private.h:103 [inline] ffff888035a24868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_clock_unregister+0x21/0x250 drivers/ptp/ptp_clock.c:415 but task is already holding lock: ffff888030704868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: n_vclocks_store+0xf1/0x6d0 drivers/ptp/ptp_sysfs.c:215 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&ptp->n_vclocks_mux); lock(&ptp->n_vclocks_mux); *** DEADLOCK *** .... ============================================ The best way to solve this is to remove the logic that checks ptp->n_vclocks in ptp_vclock_in_use(). The reason why this is appropriate is that any path that uses ptp->n_vclocks must unconditionally check if ptp->n_vclocks is greater than 0 before unregistering vclocks, and all functions are already written this way. And in the function that uses ptp->n_vclocks, we already get ptp->n_vclocks_mux before unregistering vclocks. Therefore, we need to remove the redundant check for ptp->n_vclocks in ptp_vclock_in_use() to prevent recursive locking. Fixes: 73f37068d540 ("ptp: support ptp physical/virtual clocks conversion") Signed-off-by: Jeongjun Park Acked-by: Richard Cochran Link: https://patch.msgid.link/20250520160717.7350-1-aha310510@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/ptp/ptp_private.h | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-) diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h index b336c12bb6976..f57ed0dd0aa40 100644 --- a/drivers/ptp/ptp_private.h +++ b/drivers/ptp/ptp_private.h @@ -87,17 +87,7 @@ static inline int queue_cnt(const struct timestamp_event_queue *q) /* Check if ptp virtual clock is in use */ static inline bool ptp_vclock_in_use(struct ptp_clock *ptp) { - bool in_use = false; - - if (mutex_lock_interruptible(&ptp->n_vclocks_mux)) - return true; - - if (!ptp->is_virtual_clock && ptp->n_vclocks) - in_use = true; - - mutex_unlock(&ptp->n_vclocks_mux); - - return in_use; + return !ptp->is_virtual_clock; } extern struct class *ptp_class; -- 2.39.5