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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id t66-20020a625f45000000b0056abfa74eddsm5749253pfb.147.2022.12.02.14.45.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Dec 2022 14:45:02 -0800 (PST) Date: Fri, 2 Dec 2022 14:45:01 -0800 From: Kees Cook To: jeffxu@chromium.org Cc: skhan@linuxfoundation.org, akpm@linux-foundation.org, dmitry.torokhov@gmail.com, dverkamp@chromium.org, hughd@google.com, jeffxu@google.com, jorgelo@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, mnissler@chromium.org, jannh@google.com, linux-hardening@vger.kernel.org Subject: Re: [PATCH v3] mm/memfd: add F_SEAL_EXEC Message-ID: <202212021444.3433C0E5@keescook> References: <20221202013404.163143-1-jeffxu@google.com> <20221202013404.163143-2-jeffxu@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221202013404.163143-2-jeffxu@google.com> X-Spamd-Result: default: False [5.33 / 9.00]; SORBS_IRL_BL(3.00)[209.85.216.43:from]; SUSPICIOUS_RECIPS(1.50)[]; SUBJECT_HAS_UNDERSCORES(1.00)[]; BAYES_HAM(-0.77)[77.38%]; MID_RHS_NOT_FQDN(0.50)[]; RCVD_NO_TLS_LAST(0.10)[]; MIME_GOOD(-0.10)[text/plain]; BAD_REP_POLICIES(0.10)[]; TO_DN_NONE(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_TWELVE(0.00)[14]; ARC_NA(0.00)[]; R_DKIM_ALLOW(0.00)[chromium.org:s=google]; MIME_TRACE(0.00)[0:+]; PREVIOUSLY_DELIVERED(0.00)[linux-mm@kvack.org]; DMARC_POLICY_ALLOW(0.00)[chromium.org,none]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TAGGED_RCPT(0.00)[]; DKIM_TRACE(0.00)[chromium.org:+]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; RCVD_COUNT_THREE(0.00)[3]; R_SPF_ALLOW(0.00)[+ip4:209.85.128.0/17]; RCVD_VIA_SMTP_AUTH(0.00)[] X-Rspamd-Queue-Id: 20EAA18000E X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: 87tny7dta1yybmk9tamdq1eu48pynbnb X-HE-Tag: 1670021103-635677 X-Bogosity: Ham, tests=bogofilter, spamicity=0.001201, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Dec 02, 2022 at 01:33:59AM +0000, jeffxu@chromium.org wrote: > From: Daniel Verkamp > > The new F_SEAL_EXEC flag will prevent modification of the exec bits: > written as traditional octal mask, 0111, or as named flags, S_IXUSR | > S_IXGRP | S_IXOTH. Any chmod(2) or similar call that attempts to modify > any of these bits after the seal is applied will fail with errno EPERM. > > This will preserve the execute bits as they are at the time of sealing, > so the memfd will become either permanently executable or permanently > un-executable. > > Co-developed-by: Jeff Xu > Signed-off-by: Jeff Xu > Signed-off-by: Daniel Verkamp Oh, one note on tag ordering here. Since you're sending it, I would expect this to read as: From: Daniel Verkamp ... Signed-off-by: Daniel Verkamp Co-developed-by: Jeff Xu Signed-off-by: Jeff Xu -- Kees Cook