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Fri, 21 Apr 2023 09:06:28 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 7mLOOhRSQmS0QwAAMHmgww (envelope-from ); Fri, 21 Apr 2023 09:06:28 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 86ED4A0729; Fri, 21 Apr 2023 11:06:28 +0200 (CEST) Date: Fri, 21 Apr 2023 11:06:28 +0200 From: Jan Kara To: Lorenzo Stoakes 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: <20230421090628.347b6qojxvfsgoqk@quack3> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: fsbska67zxgkgdadbrd5b3k6e4z86yeu X-Rspamd-Queue-Id: 3BE1A2000F X-HE-Tag: 1682067989-660936 X-HE-Meta: U2FsdGVkX18XQb6cTM+pwef/sdVipfXkR2AG0sbLsPSHGkFQPp74SOWQeBNU4K1nkD+U77cGX8PKDKO1lbG0Y3IIuM3btHgwlGmDzssaJURVUpVfmMN0bkQXpceNfrE+D51YAt9TCVePAM26R/P9dSjDoqgUGcf3PxAQaQ0FuWtXG9AYmJ4ALi6MJt0rBFcclusuk/1F+7hrLj1jzSu+XiBmPdNngCBhvg5F5lsfrvI0w9CZzWNEKhwjMrMLb6N+SSgifaEj7AEA8XnJBw4sUk3rUGj71sm/MSskRLKDehhA/MqNrp/FvBeb41IHtTR8ekFB4WCeDTI4CAWOCrdPSsMA1Jw0EPG56rKG+rAmWAMFiuUEDFpYsAEbpw64fFagtjeamvvhxsX36RfxeVWiVqJiMCbiSBk2EM6PEy0EGKrachFTnkY0Kr+UrfjnMotl3rZwo1OuPazfKDvRyuB5tcn1inuJ8D5i3zY8FjR7Fo00tbdWq02zwofZxv6RHo2D8AhwJQS959a45kJRDbmEyYjPI+y9VjRCZccf+IyMcZHLLmFTdy7P7CRcG5I1DMtUD6806LmeeWCsw+NA5WM9mbydShrNBcNZeI7LdTlFV4q2bO0pfDwAkafFcaszMbhB9GPiJXwucp0DHHEtUgwjP2pC6rQKhfVADir3k2Eg8lNlEmpsmCVHJsCpV71bwRmPkLfzrqiaV79MSFOdAGvhkCSvg+mW30ey65UR/a45oufDSQKjkb75sGI9psyweeiPtb9h59B35DiRjgARsVBDmjkF8zJ0w9D7dtbfr1C7KI9gw9d2WizPMcx0ePC6UxMl5esgiHPZ2cwcugBKnJNNDkfdwkrLsH85FOi5QIbL4GFogct75fqKwRlnKBP/t9fCTq/vbapz2lXvtwd7/1M4QBRjZS1GoFpFpEnUiH+T/MQVZ4izMPwA895wZuSBatYdM4E78BsStMbh08+7KpU CHzA09w8 HPg9/MIWlvb/dFHW5E+/4Sx4W+X8tp/0ioVq7DNvCB2bSMushUSru/ShqT8zqOYK29kA3tqLDk6tXDvaX2Ji/JNnggK1EddfNALV2zZSEJqSOLKQVs0kgHxbabkiOv+q2C9015cSvFUc0NkYAwvd9XMdHmEBaRHXxSo4OSiU2O0eG6j2T3L7MAn2cYs+F/62hapouTPssbuUYwf8zSp0dvaaDr3TeH7nn+ic0E6XiqjNWJlJ9nXszrujnnbaQWFl9jFku9gMaNcaANAjnxb0N+zulrZAyyqYt3vxjicPqgAplfvF/XORcmzdtsXqEPPfW8sHH 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 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? Honza -- Jan Kara SUSE Labs, CR