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From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: "Michał Mirosław" <emmir@google.com>,
	"Andrei Vagin" <avagin@gmail.com>,
	"Danylo Mocherniuk" <mdanylo@google.com>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Suren Baghdasaryan" <surenb@google.com>,
	"Greg KH" <gregkh@linuxfoundation.org>,
	"Christian Brauner" <brauner@kernel.org>,
	"Peter Xu" <peterx@redhat.com>, "Yang Shi" <shy828301@gmail.com>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Zach O'Keefe" <zokeefe@google.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	kernel@collabora.com,
	"Gabriel Krisman Bertazi" <krisman@collabora.com>,
	"David Hildenbrand" <david@redhat.com>,
	"Peter Enderborg" <peter.enderborg@sony.com>,
	"open list : KERNEL SELFTEST FRAMEWORK"
	<linux-kselftest@vger.kernel.org>,
	"Shuah Khan" <shuah@kernel.org>,
	"open list" <linux-kernel@vger.kernel.org>,
	"open list : PROC FILESYSTEM" <linux-fsdevel@vger.kernel.org>,
	"open list : MEMORY MANAGEMENT" <linux-mm@kvack.org>,
	"Paul Gofman" <pgofman@codeweavers.com>
Subject: Re: [PATCH v6 2/3] fs/proc/task_mmu: Implement IOCTL to get and/or the clear info about PTEs
Date: Mon, 12 Dec 2022 23:42:16 +0300	[thread overview]
Message-ID: <Y5eSKBJ9hTtw9cbK@grain> (raw)
In-Reply-To: <20221109102303.851281-3-usama.anjum@collabora.com>

On Wed, Nov 09, 2022 at 03:23:02PM +0500, Muhammad Usama Anjum wrote:
...
> +
> +static long do_pagemap_sd_cmd(struct mm_struct *mm, struct pagemap_scan_arg *arg)
> +{
> +	struct mmu_notifier_range range;
> +	unsigned long __user start, end;
> +	struct pagemap_scan_private p;
> +	int ret;
> +
> +	start = (unsigned long)untagged_addr(arg->start);
> +	if ((!IS_ALIGNED(start, PAGE_SIZE)) || (!access_ok((void __user *)start, arg->len)))
> +		return -EINVAL;
> +
> +	if (IS_GET_OP(arg) &&
> +	    ((arg->vec_len == 0) || (!access_ok((struct page_region *)arg->vec, arg->vec_len))))
> +		return -ENOMEM;
> +
> +	if (IS_SD_OP(arg) && ((arg->required_mask & PAGEMAP_NONSD_OP_MASK) ||
> +	     (arg->anyof_mask & PAGEMAP_NONSD_OP_MASK)))
> +		return -EINVAL;
> +
> +	end = start + arg->len;
> +	p.max_pages = arg->max_pages;
> +	p.found_pages = 0;
> +	p.flags = arg->flags;
> +	p.required_mask = arg->required_mask;
> +	p.anyof_mask = arg->anyof_mask;
> +	p.excluded_mask = arg->excluded_mask;
> +	p.return_mask = arg->return_mask;
> +	p.vec_index = 0;
> +	p.vec_len = arg->vec_len;
> +
> +	if (IS_GET_OP(arg)) {
> +		p.vec = vzalloc(arg->vec_len * sizeof(struct page_region));
> +		if (!p.vec)
> +			return -ENOMEM;
> +	} else {
> +		p.vec = NULL;
> +	}

Hi Muhammad! I'm really sorry for diving in such late (unfortunatelly too busy to
step in yet). Anyway, while in general such interface looks reasonable here are
few moments which really bothers me: as far as I undertstand you don't need
vzalloc here, plain vmalloc should works as well since you copy only filled
results back to userspace. Next -- there is no restriction on vec_len parameter,
is not here a door for DoS from userspace? Say I could start a number of ioctl
on same pagemap and try to allocate very big amount of vec_len in summay causing
big pressure on kernel's memory. Or I miss something obvious here?

  parent reply	other threads:[~2022-12-12 20:42 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-09 10:23 [PATCH v6 0/3] Implement IOCTL to get and/or the clear info about PTEs Muhammad Usama Anjum
2022-11-09 10:23 ` [PATCH v6 1/3] fs/proc/task_mmu: update functions to clear the soft-dirty PTE bit Muhammad Usama Anjum
2022-11-09 10:23 ` [PATCH v6 2/3] fs/proc/task_mmu: Implement IOCTL to get and/or the clear info about PTEs Muhammad Usama Anjum
2022-11-09 23:54   ` Andrei Vagin
2022-11-11 10:10     ` Muhammad Usama Anjum
2022-11-10 17:58   ` kernel test robot
2022-11-11 17:13   ` kernel test robot
2022-11-11 17:53     ` Muhammad Usama Anjum
2022-11-18  1:32   ` kernel test robot
2022-12-12 20:42   ` Cyrill Gorcunov [this message]
2022-12-13 13:04     ` Muhammad Usama Anjum
2022-12-13 22:22       ` Cyrill Gorcunov
2022-11-09 10:23 ` [PATCH v6 3/3] selftests: vm: add pagemap ioctl tests Muhammad Usama Anjum
2022-11-09 10:34 ` [PATCH v6 0/3] Implement IOCTL to get and/or the clear info about PTEs David Hildenbrand
2022-11-11  7:08   ` Muhammad Usama Anjum
2022-11-14 15:46     ` David Hildenbrand
2022-11-21 15:00       ` Muhammad Usama Anjum
2022-11-21 15:55         ` David Hildenbrand
2022-11-30 11:42           ` Muhammad Usama Anjum
2022-11-30 12:10             ` David Hildenbrand
2022-12-05 15:29               ` Muhammad Usama Anjum
2022-12-05 15:39                 ` David Hildenbrand
2022-11-23 14:11 ` Peter Xu

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