From: Yafang Shao <laoar.shao@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH] mm, gpu: fix error when FOLL_MLOCK an unpresent page
Date: Mon, 30 Aug 2021 18:55:02 +0800 [thread overview]
Message-ID: <CALOAHbB8YSBUwwU2S6vBbhUPzEezNXgaPfhzJzBA6X5zfaRW+g@mail.gmail.com> (raw)
In-Reply-To: <YSyuB11GjXg4MBig@infradead.org>
On Mon, Aug 30, 2021 at 6:08 PM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Mon, Aug 30, 2021 at 05:12:32PM +0800, Yafang Shao wrote:
> > > Which is not a valid way to call get_user_pages. What we need to do is
> > > to reject that case.
> >
> > Do you mean below change ?
>
> Sory of. I think once touching this we should do a few more cleanups
> including making many of the flags private to gup.c. I'll try to find
> some time to post a more complete series.
JFYI, below test case can also hit the bug I reported above.
#define _GNU_SOURCE
#include <stdio.h>
#include <sys/mman.h>
#define LEN 4096
int main()
{
char *addr;
int ret;
addr = mmap(NULL, LEN, PROT_READ|PROT_WRITE, MAP_PRIVATE |
MAP_ANON , -1, 0);
if (addr == MAP_FAILED) {
perror("mmap");
return ret;
}
/*
* MLOCK_ONFAULT will hit below if condition.
* if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
* return -ENOENT;
*/
ret = mlock2(addr, LEN, MLOCK_ONFAULT);
// ret = mlock2(addr, LEN, 0);
if (ret < 0) {
perror("mlock2");
return ret;
}
return 0;
}
--
Thanks
Yafang
next prev parent reply other threads:[~2021-08-30 10:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-29 1:19 [PATCH] mm, gpu: fix error when FOLL_MLOCK an unpresent page Yafang Shao
2021-08-30 7:00 ` Christoph Hellwig
2021-08-30 9:12 ` Yafang Shao
2021-08-30 10:08 ` Christoph Hellwig
2021-08-30 10:55 ` Yafang Shao [this message]
2021-08-31 1:36 ` Kirill A. Shutemov
2021-08-31 12:32 ` Yafang Shao
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