From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.128.181 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794347863; b=cIkHQk9ecpJiJIZL3BB1bLcu84GQls09ZiJkvGMblaaYzj19zewiba9V9M3OYQhZjK56 Gnzxv0NuaZ7IVDdXxTArF7G5wDYcwRdk8exhzm13Kr2CMoAVq56GKEcHEQ+eC3aCgqvWQ oHAKlh4Kp5PJ0sg4QovqRWC42PVMaFnrMgsj6HftRJ10f22HyGylRkarqnYRkMzw6SRcj 7+n0J7fzTd5bE0i0lgK5DvTYCjV3mVI5/+4HJ6EQBgIWx4upcu5v2uHZnkl5ZA/tq6pXW yUC7ezfzXGtzXTdU5lRdgFChKlOHtQw+8XWauCBG98dN5VENNqKVU8SsqCFmXadMJ5w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794347863; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: From:To:Cc:Subject:Date:Message-ID:X-Mailer:MIME-Version: Content-Transfer-Encoding; bh=KtNiiE9TTBKD7Se2r/k45iohaRRy+fN+xVDbL1SGOtg=; b=mLUt7d+QWjCp6bLiK8ch2GErNLCxAsMcXTxSvVSzDagb6ZI7B/gcPTed9yqppe60EKd7 qSw4el2Mr3aJnpox2gHcUF67MbN1p+kiTR/qRDPyONkGRwL82Tq8EgIPGsoywke7AyYs9 VPUhxMR/j2g0PtHwuT+LIrVmS8ovK4SLfUgoOwrdtIkazo0up2ln3R9MyLOnRy6MfHiew aBXoVwxaYX/wtsTu2scrocVI87oGCaMeDhnSEuz7tYiUz3LPs/mJJUFBAi+caR/NWZFuc /jCPhGKXSzxIAWTPAjI2zkl2CEbnorTTF2AXSkQ8CrDxKVhKv7hX/JZJTJeKt0E1ycw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=rYdAUEGa; arc=none smtp.remote-ip=209.85.128.181 Received: from mail-yw1-f181.google.com (mail-yw1-f181.google.com [209.85.128.181]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4BE8C60A2614 for ; Tue, 10 Nov 2026 21:57:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 4BE8C60A2614 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.a=rsa-sha256 header.s=20260707 header.b=rYdAUEGa Received: by mail-yw1-f181.google.com with SMTP id 00721157ae682-8b10d24345dso26409077b3.3 for ; Tue, 10 Nov 2026 13:57:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20260707; t=1794347862; x=1794952662; 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:content-type; bh=KtNiiE9TTBKD7Se2r/k45iohaRRy+fN+xVDbL1SGOtg=; b=rYdAUEGayiJdOKCxNPQLEpQR5kU5VPdw5jnM7jQQwdaXvGiVR/TF0WdMqnhnpeHUWo josep6Xf1xx5+U3fFudBb9taGXUUKk/VU1fKLQKAfQgurzMqfpgaaMZCLJPV2/OYHiek MhLEcZ4XXsCtRa9dZ2eEto5ZWudLGNPruwrCrJm75bBjpQ8IVRzzDQV95FKHaABdpnHL mXbA3JRmahUbVKmYUH7OfudaUYhcc+Tmdr7tMWHDRvRqSf2PYD41lz4NOBP26GXQlwqp fbA1QpLgjCOQuFsfx7+lnoCvNlS+13TkXbstn7DC5QrVAxenqdBaiPCcm+QzkGUpsam9 3Pog== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1794347862; x=1794952662; 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:content-type; bh=KtNiiE9TTBKD7Se2r/k45iohaRRy+fN+xVDbL1SGOtg=; b=CyLDRtypDzaSmdZSszN1lovVNIrkysKgurYh5XAKowRT198urZMKfyfy9X8+qho9kT nV2e8+H7j5PoXo4mpKsxokbnoLznhTlXF7rbM8orn5gzwP25jpEvG86Lb7UPNeEhwgd4 j1PcVK1YE9ZEJVxyYKnkUNHVKODmOB/32TZPeAye8mBk7zh2FsUzr0EbEn4fijV/NV7S 8+PWjWyd4fmtseJmZuRJ7bjIL0U66Rfq6Fdh81LiSGZFYTXBXOqlTTpqo9qp7jBC6DJR 4inDYBEUIHGNxOglajti8XKeF2P3TSKdhZ+eKwUrxzrBbETq/0UVPD5LNqI9gd4h9QqP ZyRA== X-Forwarded-Encrypted: i=1; AL+hErGJakypbDPJwxCwqex5ENcV/5tlbh6gOHG1sYcNa4mwwF3RpOtx0k4JiTTebt/ZTEv0ykZMLhuoh/+Xk0o=@vger.kernel.org X-Gm-Message-State: APuU4Z85gic8lJUkdz9q4DB6TZxFE5L/LMGSB8Xv5p/mnjTFnGqlsuDF A5g1F1/hF2HKRtylgK5fRPdJYkbOh1xO2+AZb+CoTz0QZ94dukF344uB X-Gm-Gg: AYBFou3JoDLCz0bb+8Loy3Dw+TMqB+NrAsV7YICrT8IE6e6SS26ewSgttGGuq6tsea8 vhMkcvjhXJh32hGHt1YxpV2WITNQQ/1RxqTt8aAPNxFk3kY1A2nr9dsp635vlGbDe1wZ6jkuSCn Un2OoOcyMj/go+ai5/6MgXxEIEG5o+l8iDcEmh6eTqYBh0knq9EDelkR9IJMVcHcFN2H7z+xGY6 IDKfbWdAHjR48DfxjSdDXsnww/+Xy/EBwVZC/S4F2/eCAqKQcjmLAMUGkKEghV1VXjfA7FO3JIf aV4Va87mqt40S/ybpHGx6vP6HwQGq67Lm6r+bzG/8vgd1bqIHZ5bVPZzCpyv3MgyvfWHHnQrNvH IskVwwXuaTKQSWyiOihFdJXl3YKYSlZ1F3mFmxbKyoFNP9wirffPErmDffFzT5TQGMv2Sj+k2/d gEqLQXvjnZr0h0dwfDC77SCQhtNOqYqLF+cybFT8wlGA1BnoJ0kPbw4atoNHFsTbpYjbspxEABy 20vESK3t1sW9ma4Ren29OtDaMpR/+TUfmzbr2WhWVVD3sTAjb2Boks24ZlK2dvhWWbe4Noj2F0m uxBAXRNYDcgtwZzTsZaEGivHbFFXo0vCv/UyyK0Z0G8ieL6Qwr391v1hX5PeqCCLmGQS8SBb8Ta S2jpISf1E X-Received: by 2002:a05:690c:e20c:10b0:8b3:34b6:4bb6 with SMTP id 00721157ae682-8b3a7e06f27mr3032297b3.5.1794347861960; Tue, 10 Nov 2026 13:57:41 -0800 (PST) Received: from fedora ([187.120.157.132]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8b3933d365fsm29877687b3.20.2026.11.10.13.57.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Nov 2026 13:57:41 -0800 (PST) From: Guilherme Giacomo Simoes To: josef@toxicpanda.com, axboe@kernel.dk Cc: linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org, Guilherme Giacomo Simoes , syzbot+d7d72f3d467710442af0@syzkaller.appspotmail.com Subject: [PATCH] nbd: fix circular lock dependency Date: Tue, 10 Nov 2026 18:57:23 -0300 Message-ID: <20261110215723.199948-1-trintaeoitogc@gmail.com> X-Mailer: git-send-email 2.52.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit nbd_genl_reconnect_sock_cb() replaces a dead socket with a new one obtained through nbd_get_socket(), but unlike nbd_add_socket() it never runs the socket through nbd_reclassify_socket(). The replacement socket therefore keeps the generic sk_lock-AF_INET/AF_INET6/AF_UNIX lock class instead of the NBD-specific class leading to a possible lock dependency. Move the reclassification into nbd_get_socket(), the single place where sockets are acquired for NBD, so both the connect and reconnect paths reclassify the socket. nbd_add_socket() no longer needs to do it. Reported-by: syzbot+d7d72f3d467710442af0@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=d7d72f3d467710442af0 Fixes: d532cddb6c60 ("nbd: Reclassify sockets to avoid lockdep circular dependency") Signed-off-by: Guilherme Giacomo Simoes --- drivers/block/nbd.c | 66 +++++++++++++++++++++++++-------------------- 1 file changed, 37 insertions(+), 29 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index ffce519bf008..bc74ddb1d9d1 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1210,34 +1210,6 @@ static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx, return ret; } -static struct socket *nbd_get_socket(struct nbd_device *nbd, unsigned long fd, - int *err) -{ - struct socket *sock; - - *err = 0; - sock = sockfd_lookup(fd, err); - if (!sock) - return NULL; - - if (!sk_is_tcp(sock->sk) && - !sk_is_stream_unix(sock->sk)) { - dev_err(disk_to_dev(nbd->disk), "Unsupported socket: should be TCP or UNIX.\n"); - *err = -EINVAL; - sockfd_put(sock); - return NULL; - } - - if (sock->ops->shutdown == sock_no_shutdown) { - dev_err(disk_to_dev(nbd->disk), "Unsupported socket: shutdown callout must be supported.\n"); - *err = -EINVAL; - sockfd_put(sock); - return NULL; - } - - return sock; -} - #ifdef CONFIG_DEBUG_LOCK_ALLOC static struct lock_class_key nbd_key[3]; static struct lock_class_key nbd_slock_key[3]; @@ -1274,6 +1246,43 @@ static void nbd_reclassify_socket(struct socket *sock) static inline void nbd_reclassify_socket(struct socket *sock) {} #endif +static struct socket *nbd_get_socket(struct nbd_device *nbd, unsigned long fd, + int *err) +{ + struct socket *sock; + + *err = 0; + sock = sockfd_lookup(fd, err); + if (!sock) + return NULL; + + if (!sk_is_tcp(sock->sk) && + !sk_is_stream_unix(sock->sk)) { + dev_err(disk_to_dev(nbd->disk), "Unsupported socket: should be TCP or UNIX.\n"); + *err = -EINVAL; + sockfd_put(sock); + return NULL; + } + + if (sock->ops->shutdown == sock_no_shutdown) { + dev_err(disk_to_dev(nbd->disk), "Unsupported socket: shutdown callout must be supported.\n"); + *err = -EINVAL; + sockfd_put(sock); + return NULL; + } + + /* + * NBD sockets are used from block/swap/writeback context, which can + * already hold locks that fs_reclaim depends on. Give them their own + * lockdep class so that a page fault on an unrelated userspace socket + * (sk_lock -> mmap_lock) is not chained to the NBD socket lock. + */ + if (sock) + nbd_reclassify_socket(sock); + + return sock; +} + static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg, bool netlink) { @@ -1296,7 +1305,6 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg, sock = nbd_get_socket(nbd, arg, &err); if (!sock) return err; - nbd_reclassify_socket(sock); if (!netlink && !nbd->task_setup && !test_bit(NBD_RT_BOUND, &config->runtime_flags)) -- 2.52.0