From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f47.google.com (mail-ed1-f47.google.com [209.85.208.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B982F346FAE for ; Mon, 16 Mar 2026 09:28:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773653319; cv=none; b=UiFpEUELZK16GedJktKigPF6nqbkNEEl9wUyOqovltSS9st5w6C+NgAd/z5W9ZAYKTvvlezrdn93HUIA2skNMSooE4AwuMGpcT7APOvnMGS1hJR8pxgj57RonHZuD4eHuB/aFZx60UqQylYim3laklrqngOnJB4HFyHsyxNMB0E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773653319; c=relaxed/simple; bh=oQzzFAMCttNUJVUfDwf/erlmu1VPa/A4aDaVaPX++84=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=pwN9weeMDUnqn8wO4fzQCyNTi7V3FjGgu+1Jh0H1jxHoPT4VwKJyGZUfx32cfduRDo1q/s4LLy3vk7BlKl6fdM+7hatjI2fxtACckb9+1tZ/7Dk6lhuFEx+M7za7PE+swlCBXTAHSH8CYaJCxskx7FaBTdwwmUBN0lUYieIhdlg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=j3uZs2K6; arc=none smtp.client-ip=209.85.208.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="j3uZs2K6" Received: by mail-ed1-f47.google.com with SMTP id 4fb4d7f45d1cf-661b08b04deso4709841a12.2 for ; Mon, 16 Mar 2026 02:28:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773653316; x=1774258116; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=C2/IwV2vEnvqLSZJL+1QuzLYnReiJ7GcK2/btvbYBlw=; b=j3uZs2K6iYR9CL11l+Dd8i/kCLUVm42UXiMxQz3moarrYB/WIXdzF8iROQf3IIlO1k b2fTC6DEQr2adHYwCc+KdsRikhrVMvIpn66YuvDXF8PelYuH59JVrvuRK09YbJyGKln4 hSCvoGZe1oyCzf8FyQCx4wxchoCIObbR2/Gzvgzo6qq/73jvPtrwufPlV7K/C/Nkhh38 wB1c5la/igKfKNSidpJIaaNErkOHgDeZeTeIXU8ETIrdeAo82mjzVZ/bhlGpQIP/adeT XD4z27G1G3UoSqfVxRYspaNrivxIJUArakpe+o8cFXlKVwcEmQqbsmapeuwx3gJiyz0i b3Nw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773653316; x=1774258116; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=C2/IwV2vEnvqLSZJL+1QuzLYnReiJ7GcK2/btvbYBlw=; b=f6dIckBMXVuwwkP2OiQJ1XT3CbC9uz3Oi1iCOQ1y6Xw7D7pdUqGR2xqt5KkPiI8tAR PhRt+B5uWmKn/ZmddiSx2TGrprPu9bgGGMZMPM4tOoOgb3o0wMe3URtvPbBFwqnBwgp8 r4q2POlXoMzV6KzhzlhCy4kG/79a3j1VFjGJg4KCgumk21PJnz5YJFke2SHafumHvcaV SYmGtQdE4uC23k/hzlmvCD5WukRGe/qWXFqeedSQ5iQx9iqHB4qPXZYmAFJ6LEnVrgfn QvUmuTwSvwgIsplxJH97cpjVN0ETalenA9k9gzHLXYf0g5aMM9exJdiPDlTwPVgS88pX CX4g== X-Forwarded-Encrypted: i=1; AJvYcCUQMfudAiMEgQif3QYftsckdzUUkRdUfB2pzyv3OmismzcQeatq404BqJeKHSMqWnCuRH3mAI4=@vger.kernel.org X-Gm-Message-State: AOJu0YxH9Je86lzVwYYvDiNsJSvD4UZ+fRlafDjIA3SoB7UkYgHSW0Wj u4vrwpwxWXu/3fQVTHaSnmdX6fDCcy9SHF/YekxsS8yIS/jYhM6V2F8k X-Gm-Gg: ATEYQzxh0y8CISDSclUPHoeh0jfdLECWphz/0EV5jGzuNsDzuG+E6nJXdrS6weIiAs/ bMIa1wVxmQ3RqNRUcXiC5ro8gdY5iU7KcWi63yv/4ldyNg2Tt3rpLMWvfMP0p1C4Z6mv1hsv51K 7G72Qq2zRw1seYbVlnCgmr2yNGbsKqzDh7uoKpVyu5tDCGj7v/jPMvFTiCzkvY4HYwy1OWt9cAO OR9hRySRxH4oCPmQS9nWplAVKKqJskfqE6MKobJfNph8HGEWt4GfayUC6L6VyDkBMVtvjOZj34m v6gBsWKZ7Jgc7YkqnPGQ8ij1TXClUHZ6e7yHI7xjDEQX5MPpS4U79lnDCL59O/hLO/Hj0GyW7jn G0Z6ok3sNf1VL9SmO4KtXkGymDbB40+0jffF6DuvjIAPkAZJSaz72O33hwy5E6k6jy+BNrQRkP7 Jc66OvbjipgvTq9Q== X-Received: by 2002:a05:6402:1476:b0:660:a2df:ad1 with SMTP id 4fb4d7f45d1cf-663ba0e9e6dmr7669579a12.7.1773653315826; Mon, 16 Mar 2026 02:28:35 -0700 (PDT) Received: from gmail.com ([2a09:bac5:4e24:2e3c::49b:47]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-663509919c9sm4892225a12.23.2026.03.16.02.28.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2026 02:28:35 -0700 (PDT) From: Qingfang Deng To: linux-ppp@vger.kernel.org, Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: James Chapman Subject: [PATCH net-next] ppp: require callers of ppp_dev_name() to hold RCU Date: Mon, 16 Mar 2026 17:28:23 +0800 Message-ID: <20260316092824.479149-1-dqfext@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ppp_dev_name() holds the RCU read lock internally to protect pch->ppp. However, as it returns netdev->name to the caller, the caller should also hold either RCU or RTNL lock to prevent the netdev from being freed. The only two references of the function is in the L2TP driver, both of which already hold RCU. So remove the internal RCU lock and document that callers must hold RCU. Signed-off-by: Qingfang Deng --- drivers/net/ppp/ppp_generic.c | 3 +-- include/linux/ppp_channel.h | 4 +++- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 6344c5eb0f98..0918ece061eb 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -2995,6 +2995,7 @@ int ppp_unit_number(struct ppp_channel *chan) /* * Return the PPP device interface name of a channel. + * Caller must hold RCU read lock. */ char *ppp_dev_name(struct ppp_channel *chan) { @@ -3003,11 +3004,9 @@ char *ppp_dev_name(struct ppp_channel *chan) struct ppp *ppp; if (pch) { - rcu_read_lock(); ppp = rcu_dereference(pch->ppp); if (ppp && ppp->dev) name = ppp->dev->name; - rcu_read_unlock(); } return name; } diff --git a/include/linux/ppp_channel.h b/include/linux/ppp_channel.h index ca8ad03eeef0..2f63e9a6cc88 100644 --- a/include/linux/ppp_channel.h +++ b/include/linux/ppp_channel.h @@ -72,7 +72,9 @@ extern int ppp_channel_index(struct ppp_channel *); /* Get the unit number associated with a channel, or -1 if none */ extern int ppp_unit_number(struct ppp_channel *); -/* Get the device name associated with a channel, or NULL if none */ +/* Get the device name associated with a channel, or NULL if none. + * Caller must hold RCU read lock. + */ extern char *ppp_dev_name(struct ppp_channel *); /* -- 2.43.0