From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 EB3276EB7C for ; Sun, 23 Mar 2025 21:03:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742763826; cv=none; b=i7zT9wQbD5k8LPYZsfdEakhJ/jd8FuL3QY20qlFTG4NJf88Tf9WvrKqUdbyWhxajfhE1qBwPkpZQK49G3SrchJNFg1IjuR6cUelR2bH2hvuda/WawsEVfarCZpnI0ZA9Fm0YJng/bfhRrnI8GXtKOHhQ2BF6XGqPsDe//l67D2w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742763826; c=relaxed/simple; bh=3JIOq5ochZh3ws1s6lkhbkBuciyTNdAoIUvUlBxhw4Y=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UYTbCUHcae7CtEDbFAupjHZswMR37Zv03B2vqKehcZPY90thiFbS6OdYsTI9UaRCKY6iTEmMP7NiIe2IQAl3PNAri7Lx+WaBl1z2pk/NWeHeIB/9TQ2jPG6fTsSNIbY14r5aoaKLb0RDnMT2Nn/4irG7bUn8q81cp/+sx5KPiH8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=WhA2nw0c; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WhA2nw0c" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1742763824; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5vpBGKmNly8SWNcuxVYwn8ZTG+u+mEvCdgvHyTuKsXM=; b=WhA2nw0coodqe47hmw/wk9TZGynTMbYwdhmUEf/04N3h/7qU1z1hQoQ3s17L8Ui454eLFn cxrVp6ZdjWOpLPQO7oWNFj42ogwXWNCQwfYm3D2k64Ku3zhPPfJmAaDlcNZRnQIxclpM01 1PVZtYWfvLJmPHmYCGrBW1DHGhjSihg= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-594-n1SnNG9dOo-weTbTFX0LEw-1; Sun, 23 Mar 2025 17:03:34 -0400 X-MC-Unique: n1SnNG9dOo-weTbTFX0LEw-1 X-Mimecast-MFC-AGG-ID: n1SnNG9dOo-weTbTFX0LEw_1742763812 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BA2F01801A12; Sun, 23 Mar 2025 21:03:31 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.42]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id A60EE180A803; Sun, 23 Mar 2025 21:03:26 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Sun, 23 Mar 2025 22:02:58 +0100 (CET) Date: Sun, 23 Mar 2025 22:02:52 +0100 From: Oleg Nesterov To: Mateusz Guzik Cc: syzbot , brauner@kernel.org, dhowells@redhat.com, jack@suse.cz, jlayton@kernel.org, kprateek.nayak@amd.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, netfs@lists.linux.dev, swapnil.sapkal@amd.com, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Subject: Re: [syzbot] [netfs?] INFO: task hung in netfs_unbuffered_write_iter Message-ID: <20250323210251.GD14883@redhat.com> References: <20250323184848.GB14883@redhat.com> <67e05e30.050a0220.21942d.0003.GAE@google.com> <20250323194701.GC14883@redhat.com> Precedence: bulk X-Mailing-List: netfs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Prateek, Mateusz, thanks for your participation! On 03/23, Mateusz Guzik wrote: > > On Sun, Mar 23, 2025 at 8:47 PM Oleg Nesterov wrote: > > > > OK, as expected. > > > > Dear syzbot, thank you. > > > > So far I think this is another problem revealed by aaec5a95d59615523db03dd5 > > ("pipe_read: don't wake up the writer if the pipe is still full"). > > > > I am going to forget about this report for now and return to it later, when > > all the pending pipe-related changes in vfs.git are merged. > > > > How do you ask syzbot for all stacks? Heh, I don't know. > The reproducer *does* use pipes, but it is unclear to me if they play > any role here please see the reproducer, https://syzkaller.appspot.com/x/repro.c?x=10d6a44c580000 res = syscall(__NR_pipe2, /*pipefd=*/0x400000001900ul, /*flags=*/0ul); if (res != -1) { r[2] = *(uint32_t*)0x400000001900; r[3] = *(uint32_t*)0x400000001904; } then res = syscall(__NR_dup, /*oldfd=*/r[3]); if (res != -1) r[4] = res; so r[2] and r[4] are the read/write fd's. then later memcpy((void*)0x400000000280, "trans=fd,", 9); ... memcpy((void*)0x400000000289, "rfdno", 5); ... sprintf((char*)0x40000000028f, "0x%016llx", (long long)r[2]); ... memcpy((void*)0x4000000002a2, "wfdno", 5); ... sprintf((char*)0x4000000002a8, "0x%016llx", (long long)r[4]); ... syscall(__NR_mount, /*src=*/0ul, /*dst=*/0x400000000000ul, /*type=*/0x400000000040ul, /*flags=*/0ul, /*opts=*/0x400000000280ul); so this pipe is actually used as "trans=fd". > -- and notably we don't know if there is someone stuck > in pipe code, resulting in not waking up the reported thread. Yes, I am not familiar with 9p or netfs, so I don't know either. Oleg.