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 4127B472F90 for ; Tue, 25 Aug 2026 13:21:34 +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=1787664100; cv=none; b=blvS1+AyMqAH7aGNBsFaHKKnKX/DWKcmJ9L2/RitWnZb1nMzHBaHB1ujP4Mwb/W7s3REM4+pbVGu0wayKT8IKEYJZWGA/34HXXbWS/lcO6UvwOwYyuFtUGQrorjnZ6+16dL62btqcnJYQMrkyxfuVS+fhmsZRRy6hqHqym0SdCs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787664100; c=relaxed/simple; bh=tlt6nmEpLs/0fQ0gKQrkQ2eKLUpkaqhJC9uMzs2fx/4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RhJltzCs0axbw75N0OunjDwNyirOnH2GkYN1lRKjWi3eSQJ3V3kgk1FENI8LsRPV1xO8vlenV3Ab5eU70xQyo56VpxyAMnsUl78PhbkCkWiQ6kGmW9VmwEpUGWfnodkdIlRzbmTJ8jVHnspS9frgIVJ+1HB9+JbbWbX40S3uWPw= 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=QJh0DYVN; 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="QJh0DYVN" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1787664090; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vU4d2g10zNfL1YNAIJuqPoPe4woqc1v8GpKzEdoRnpE=; b=QJh0DYVN6Z9iqQZBPIO498UllccOBPiwx4w9jTciykoN56s4by7Yb7e4MnxLYwthWxYHqw QOh2+MdcFu3djsjdQJkZHNSCYU0x48NlLRnGNHqQKJHCOQ/O5oUyaJ4NNSGtX4pa8+8mzX 9loeBG1mSqFfVa/KG2vj8xRQNXnBaE8= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-650-iJmeief9MHGExr93kMS1KA-1; Tue, 25 Aug 2026 09:21:24 -0400 X-MC-Unique: iJmeief9MHGExr93kMS1KA-1 X-Mimecast-MFC-AGG-ID: iJmeief9MHGExr93kMS1KA_1787664082 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 009BD1944D27; Tue, 25 Aug 2026 13:21:22 +0000 (UTC) Received: from warthog.com (unknown [10.44.32.15]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id A0EEB1803A44; Tue, 25 Aug 2026 13:21:18 +0000 (UTC) From: David Howells To: Christian Brauner Cc: David Howells , Paulo Alcantara , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Edward Adam Davis , syzbot+6a13fc77eb6f0802be2d@syzkaller.appspotmail.com Subject: [PATCH v2 6/9] netfs: break unbuffered write when netfs_alloc_subrequest() fails Date: Tue, 25 Aug 2026 14:20:40 +0100 Message-ID: <20260825132045.1000787-7-dhowells@redhat.com> In-Reply-To: <20260825132045.1000787-1-dhowells@redhat.com> References: <20260825132045.1000787-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 From: Edward Adam Davis syzbot reported a null-ptr-deref below [1] following a fault injection in netfs_alloc_subrequest(). [0] When netfs_alloc_subrequest() fails, subreq is NULL. Later, netfs_prepare_write() tries to initialize members of subreq(e.g., source), the issue in [1] is triggered. Let's handle the error of netfs_prepare_write() properly. [0] FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 0 Call Trace: netfs_alloc_subrequest+0x116/0x3f0 netfs_prepare_write+0x76/0x7b0 netfs_unbuffered_write+0x75c/0x2020 netfs_unbuffered_write_iter_locked+0x7d6/0xa80 netfs_unbuffered_write_iter+0x442/0x720 v9fs_file_write_iter+0xbf/0x100 vfs_write+0x6ac/0x1050 [1] KASAN: null-ptr-deref in range [0x00000000000000a8-0x00000000000000af] RIP: 0010:netfs_prepare_write+0xbc/0x7b0 fs/netfs/write_issue.c:173 Call Trace: netfs_unbuffered_write+0x75c/0x2020 fs/netfs/direct_write.c:111 netfs_unbuffered_write_iter_locked+0x7d6/0xa80 fs/netfs/direct_write.c:290 netfs_unbuffered_write_iter+0x442/0x720 fs/netfs/direct_write.c:382 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409 new_sync_write fs/read_write.c:595 [inline] [dhowells: Altered to put -ENOMEM into ret, not wreq->error] Fixes: 288ace2f57c9 ("netfs: New writeback implementation") Reported-by: syzbot+6a13fc77eb6f0802be2d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6a13fc77eb6f0802be2d Tested-by: syzbot+6a13fc77eb6f0802be2d@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis Signed-off-by: David Howells --- fs/netfs/direct_write.c | 4 ++++ fs/netfs/write_issue.c | 2 ++ 2 files changed, 6 insertions(+) diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c index fbcfadb232ee..7173ce04bac6 100644 --- a/fs/netfs/direct_write.c +++ b/fs/netfs/direct_write.c @@ -110,6 +110,10 @@ static int netfs_unbuffered_write(struct netfs_io_request *wreq) if (!subreq) { netfs_prepare_write(wreq, stream, wreq->start + wreq->transferred); subreq = stream->construct; + if (!subreq) { + ret = -ENOMEM; + break; + } stream->construct = NULL; } diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c index 2d9cfcd43658..851f6f93ad45 100644 --- a/fs/netfs/write_issue.c +++ b/fs/netfs/write_issue.c @@ -170,6 +170,8 @@ void netfs_prepare_write(struct netfs_io_request *wreq, rolling_buffer_make_space(&wreq->buffer, wreq->gfp); subreq = netfs_alloc_subrequest(wreq); + if (!subreq) + return; subreq->source = stream->source; subreq->start = start; subreq->stream_nr = stream->stream_nr;