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From: Dmitry Safonov <dima@arista.com>
To: Brian Geffon <bgeffon@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Dmitry Safonov <0x7f454c46@gmail.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@redhat.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Minchan Kim <minchan@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Vlastimil Babka <vbabka@suse.cz>, Will Deacon <will@kernel.org>,
	linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH 2/6] mm/mremap: For MREMAP_DONTUNMAP check security_vm_enough_memory_mm()
Date: Mon, 28 Dec 2020 19:12:21 +0000	[thread overview]
Message-ID: <d25ad10c-6f67-8c11-18c3-0193b8ea14c4@arista.com> (raw)
In-Reply-To: <CADyq12y4WAjT7O3_4E3FmBv4dr5fY6utQZod1UN0Xv8PhOAnQA@mail.gmail.com>

On 12/28/20 6:21 PM, Brian Geffon wrote:
> This looks good to me with a small comment.
> 
>>         if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
>>                 /* OOM: unable to split vma, just get accounts right */
>> -               if (vm_flags & VM_ACCOUNT)
>> +               if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
>>                         vm_acct_memory(new_len >> PAGE_SHIFT);
> 
> Checking MREMAP_DONTUNMAP in the do_munmap path is unnecessary as
> MREMAP_DONTUNMAP will have already returned by this point.

In this code it is also used as err-path. In case move_page_tables()
fails to move all page tables or .mremap() callback fails, the new VMA
is unmapped.

IOW, MREMAP_DONTUNMAP returns under:
:	if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) {

-- 
          Dima

  reply	other threads:[~2020-12-28 19:13 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-13  1:34 [PATCH 0/6] mremap: move_vma() fixes Dmitry Safonov
2020-10-13  1:34 ` [PATCH 1/6] mm/mremap: Account memory on do_munmap() failure Dmitry Safonov
2020-10-13  1:34 ` [PATCH 2/6] mm/mremap: For MREMAP_DONTUNMAP check security_vm_enough_memory_mm() Dmitry Safonov
2020-12-28 18:21   ` Brian Geffon
2020-12-28 19:12     ` Dmitry Safonov [this message]
2020-12-30 15:43       ` Brian Geffon
2020-10-13  1:34 ` [PATCH 3/6] mremap: Don't allow MREMAP_DONTUNMAP on special_mappings and aio Dmitry Safonov
2020-12-28 18:03   ` Brian Geffon
2020-12-28 19:33     ` Dmitry Safonov
2020-12-28 19:43       ` Dmitry Safonov
2020-10-13  1:34 ` [PATCH 4/6] vm_ops: Rename .split() callback to .may_split() Dmitry Safonov
2020-10-13  1:34 ` [PATCH 5/6] mremap: Check if it's possible to split original vma Dmitry Safonov
2020-10-13  1:34 ` [PATCH 6/6] mm: Forbid splitting special mappings Dmitry Safonov
2021-01-22 12:58   ` Will Deacon
2021-01-22 13:00     ` Will Deacon
2021-01-22 19:52       ` Dmitry Safonov

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