From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 A63C7258EF3 for ; Wed, 24 Jun 2026 11:58:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782302296; cv=none; b=KUDJ7jr5SoQ84oJ4ovBic6ixrkkAtP9tgRrtxeE9RJT2/2Beq6ujmb2OQZ71FmpYS6RhkfsYbJ0DmLupUsNKEp0NsRhSkWXXYuct9Vw+tBLLLTQbmsyqnlejFgVUxTKawqiGVkOKfJ2VashePNXADhA41CWDUVtNLQD5a8tBZ3U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782302296; c=relaxed/simple; bh=TkR3U9MBG4uQjx6fjGoDl2fjGjJJGgR5Cumzr1yedxE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bVIWNbb592R5boqp/5sbi1BY4Ma41jWD4pMpXYijNWHujXK0iLPD3vWysHaGqvrq7CqgbCXNfB41QKL8aV53WApFplgw3dE9IuCZ1ORmcudVxLPVjzQsEfFk6QWzGavTfVz3pUowSHGsym9RXizbzoQu7UEhIsRejXN4Q/U3aqY= 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=JoVUulLl; arc=none smtp.client-ip=170.10.129.124 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="JoVUulLl" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1782302293; 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=Vr1GtzsrCWNPBr/vFOn5YZqpXbdYY2IBSvhsLoG3IHw=; b=JoVUulLl7QxoyPS81cIDPgrhdGW6uuESDw6rR5SlQuUTU/Z9QZQRsKl/dw4uKZAw9r8Fis UrkflY4oXGq7C1AfSkvyFCw3hDtDZQUL9E0LivB+JbLNslQ30FGY9e8ibQ8eiFSCzFA5bC lWTYEbwLBu4FvQBka2xZGL19e7+3/z8= Received: from mx-prod-mc-01.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-341-iyJLl-RBOd2ZUZGmpnSjQw-1; Wed, 24 Jun 2026 07:58:10 -0400 X-MC-Unique: iyJLl-RBOd2ZUZGmpnSjQw-1 X-Mimecast-MFC-AGG-ID: iyJLl-RBOd2ZUZGmpnSjQw_1782302288 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0B5221955EBA; Wed, 24 Jun 2026 11:58:08 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.44.49.152]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4F3361956049; Wed, 24 Jun 2026 11:58:02 +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, Matthew Wilcox , Christoph Hellwig , Jens Axboe , Mike Marshall Subject: [PATCH v2 04/14] iov_iter: Fix potential underflow in iov_iter_extract_xarray_pages() Date: Wed, 24 Jun 2026 12:57:25 +0100 Message-ID: <20260624115737.2964520-5-dhowells@redhat.com> In-Reply-To: <20260624115737.2964520-1-dhowells@redhat.com> References: <20260624115737.2964520-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: ceph-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 In iov_iter_extract_xarray_pages(), if no pages are extracted because there's a hole (or something otherwise unextractable) in the xarray, then the calculation of maxsize at the end can go wrong if the starting offset is not zero. Fix this by returning 0 in such a case and freeing the page array if allocated here rather than being passed in. Note that in the near future, ITER_XARRAY should be removed. Fixes: 7d58fe731028 ("iov_iter: Add a function to extract a page list from an iterator") Link: https://sashiko.dev/#/patchset/20260608145432.681865-1-dhowells%40redhat.com Link: https://sashiko.dev/#/patchset/20260616100821.2062304-1-dhowells%40redhat.com Signed-off-by: David Howells cc: Paulo Alcantara cc: Matthew Wilcox cc: Christoph Hellwig cc: Jens Axboe cc: Mike Marshall cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org --- lib/iov_iter.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 243662af1af7..5f60733f3280 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1568,6 +1568,7 @@ static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i, struct folio *folio; unsigned int nr = 0, offset; loff_t pos = i->xarray_start + i->iov_offset; + bool will_alloc = !*pages; XA_STATE(xas, i->xarray, pos >> PAGE_SHIFT); offset = pos & ~PAGE_MASK; @@ -1595,6 +1596,14 @@ static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i, } rcu_read_unlock(); + if (!nr) { + if (will_alloc) { + kvfree(*pages); + *pages = NULL; + } + return 0; + } + maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize); iov_iter_advance(i, maxsize); return maxsize;