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[86.156.84.164]) by smtp.gmail.com with ESMTPSA id s13-20020adfeb0d000000b002fb6a79dea0sm5256391wrn.7.2023.04.21.14.15.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Apr 2023 14:15:13 -0700 (PDT) Date: Fri, 21 Apr 2023 22:15:12 +0100 From: Lorenzo Stoakes To: Jan Kara Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Matthew Wilcox , Mike Kravetz , Muchun Song , Alexander Viro , Christian Brauner , Andy Lutomirski Subject: Re: [RFC PATCH 3/3] mm: perform the mapping_map_writable() check after call_mmap() Message-ID: <44519d2e-8c26-4418-863f-7459d5adbc45@lucifer.local> References: <20230421090628.347b6qojxvfsgoqk@quack3> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230421090628.347b6qojxvfsgoqk@quack3> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C239D1C000F X-Stat-Signature: khn6ots6oft4e6fy7f7zo4cjj8h61kfu X-HE-Tag: 1682111716-915335 X-HE-Meta: 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 2eltP51p 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 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 Fri, Apr 21, 2023 at 11:06:28AM +0200, Jan Kara wrote: > On Mon 03-04-23 23:28:32, Lorenzo Stoakes wrote: > > In order for a F_SEAL_WRITE sealed memfd mapping to have an opportunity to > > clear VM_MAYWRITE, we must be able to invoke the appropriate vm_ops->mmap() > > handler to do so. We would otherwise fail the mapping_map_writable() check > > before we had the opportunity to avoid it. > > > > This patch moves this check after the call_mmap() invocation. Only memfd > > actively denies write access causing a potential failure here (in > > memfd_add_seals()), so there should be no impact on non-memfd cases. > > > > This patch makes the userland-visible change that MAP_SHARED, PROT_READ > > mappings of an F_SEAL_WRITE sealed memfd mapping will now succeed. > > > > Signed-off-by: Lorenzo Stoakes > > --- > > mm/mmap.c | 12 ++++++------ > > 1 file changed, 6 insertions(+), 6 deletions(-) > > > > diff --git a/mm/mmap.c b/mm/mmap.c > > index c96dcce90772..a166e9f3c474 100644 > > --- a/mm/mmap.c > > +++ b/mm/mmap.c > > @@ -2596,17 +2596,17 @@ unsigned long mmap_region(struct file *file, unsigned long addr, > > vma->vm_pgoff = pgoff; > > > > if (file) { > > - if (is_shared_maywrite(vm_flags)) { > > - error = mapping_map_writable(file->f_mapping); > > - if (error) > > - goto free_vma; > > - } > > - > > vma->vm_file = get_file(file); > > error = call_mmap(file, vma); > > if (error) > > goto unmap_and_free_vma; > > > > + if (vma_is_shared_maywrite(vma)) { > > + error = mapping_map_writable(file->f_mapping); > > + if (error) > > + goto unmap_and_free_vma; > > Shouldn't we rather jump to close_and_free_vma? You're right, we may need to call vma->vm_ops->close() to match the ->mmap(). > > Honza > -- > Jan Kara > SUSE Labs, CR