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 D4CFA2E8DE4; Tue, 17 Jun 2025 16:53:15 +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=1750179195; cv=none; b=E3rCNWateA/ExzAirR0N8UfD1mUho3hU3NLl5FItW2JA5aO+NeNPEEiDXDnSeFCWu/4OZmFvGpMsu0EBy/lFb7yq0mkBSJrrWvwbgrjBS7sg7t42AtHnapiFsu4ifYcV8XSqGqxusR5/lpUVGpUSLoMCGjsTe9oj1DHUGgDnXWc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750179195; c=relaxed/simple; bh=pIU3N+r8Jrw1pO/qT2Gbrh23fCUZ6zYnZd4yxuQbqtA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aJP2SF/fB9S8wICn1qpjpVPj5AKEOpI8J5r/PwoOjZQnY7cHwWU3qLUHHjb96BCEpqGB09gbGEODMhjUGawlqtzakQNo+v3CFOTiwtdVsQ8B5jVZa7JpAptT51UYfnKlC2fc4+br0EnMfAMwpeM+X550Ctz6lkxRpGqCMsYAaPQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hexqkJMs; 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="hexqkJMs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44DA9C4CEE3; Tue, 17 Jun 2025 16:53:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750179195; bh=pIU3N+r8Jrw1pO/qT2Gbrh23fCUZ6zYnZd4yxuQbqtA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hexqkJMsRSQ+OyEFzH4c2Hc74Rnj35sANLYobTt9RisVwi1aP4msaYg9s8vLUtCdg kVC8nxe0MnuVwAr5XcGgU/UdoVsRPR8DVSt2yUV6GcUJZIO9GAQzY89mkCGUq0DpsI YzzI84ntN5XZwDofztRL0wnVy5BuZ0dMNr9rrEOg= 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 6.15 670/780] ptp: remove ptp->n_vclocks check logic in ptp_vclock_in_use() Date: Tue, 17 Jun 2025 17:26:18 +0200 Message-ID: <20250617152518.749820136@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250617152451.485330293@linuxfoundation.org> References: <20250617152451.485330293@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 6.15-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 18934e28469ee..528d86a33f37d 100644 --- a/drivers/ptp/ptp_private.h +++ b/drivers/ptp/ptp_private.h @@ -98,17 +98,7 @@ 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; } /* Check if ptp clock shall be free running */ -- 2.39.5