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Shutemov" To: Jakub =?utf-8?Q?Mat=C4=9Bna?= Cc: linux-mm@kvack.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org, vbabka@suse.cz, mhocko@kernel.org, mgorman@techsingularity.net, willy@infradead.org, liam.howlett@oracle.com, hughd@google.com, riel@surriel.com, rostedt@goodmis.org, peterz@infradead.org, david@redhat.com Subject: Re: [RFC PATCH v3 2/6] [PATCH 2/6] mm: add merging after mremap resize Message-ID: <20220520134124.6glbfzhrgzutfor6@box.shutemov.name> References: <20220516125405.1675-1-matenajakub@gmail.com> <20220516125405.1675-3-matenajakub@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220516125405.1675-3-matenajakub@gmail.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A8B9E1C001F X-Stat-Signature: x3ybyrmof8fskg4hdjgj6q35j6bj9n7x Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=shutemov-name.20210112.gappssmtp.com header.s=20210112 header.b=6qt22nK9; dmarc=none; spf=none (imf21.hostedemail.com: domain of kirill@shutemov.name has no SPF policy when checking 209.85.167.48) smtp.mailfrom=kirill@shutemov.name X-Rspam-User: X-HE-Tag: 1653053963-537134 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, May 16, 2022 at 02:54:01PM +0200, Jakub Matěna wrote: > When mremap call results in expansion, it might be possible to merge the > VMA with the next VMA which might become adjacent. This patch adds > vma_merge call after the expansion is done to try and merge. > > Signed-off-by: Jakub Matěna > --- > mm/mremap.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index 303d3290b938..75cda854ec58 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -9,6 +9,7 @@ > */ > > #include > +#include > #include > #include > #include > @@ -1022,8 +1023,10 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, > } > } > > - if (vma_adjust(vma, vma->vm_start, addr + new_len, > - vma->vm_pgoff, NULL)) { > + if (!vma_merge(mm, vma, addr + old_len, addr + new_len, > + vma->vm_flags, vma->anon_vma, vma->vm_file, > + vma->vm_pgoff + (old_len >> PAGE_SHIFT), vma_policy(vma), > + vma->vm_userfaultfd_ctx, anon_vma_name(vma))) { Hm. Don't you need to update 'vma' with result of vma_merge()? 'vma' is used below the point and IIUC it can be use-after-free. -- Kirill A. Shutemov