From: Matthew Wilcox <willy@infradead.org>
To: David Hildenbrand <david@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>,
"maple-tree@lists.infradead.org" <maple-tree@lists.infradead.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Liu Zixian <liuzixian4@huawei.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] mm/mmap: Fix MAP_FIXED address return on VMA merge
Date: Tue, 18 Oct 2022 20:58:28 +0100 [thread overview]
Message-ID: <Y08FZMg1Kgr++o5D@casper.infradead.org> (raw)
In-Reply-To: <3da4244a-5a1b-cf34-bf5c-22c199b15cb6@redhat.com>
On Tue, Oct 18, 2022 at 09:27:11PM +0200, David Hildenbrand wrote:
> > + if (WARN_ON((addr != vma->vm_start))) {
> > + error = -EINVAL;
> > + goto close_and_free_vma;
> > + }
>
> If this is something that user space can trigger, WARN_* is the wrong
> choice. But what I understand from the comment change is that this must not
> happen at that point unless there is a real issue.
It's something that a device driver can trigger. So if userspace calls
mmap(MAP_FIXED) and the driver decides to overwrite the vma->vm_start,
it'll trigger. I think WARN_ON() is the right choice.
> Why not "if (WARN_ON_ONCE)" ?
Because by it's nature it's not going to trigger a bajillion times in
quick succession.
next prev parent reply other threads:[~2022-10-18 19:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-18 19:17 Liam Howlett
2022-10-18 19:27 ` David Hildenbrand
2022-10-18 19:58 ` Matthew Wilcox [this message]
2022-10-18 20:25 ` Liam Howlett
2022-10-19 14:08 ` David Hildenbrand
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