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Mon, 26 Oct 2026 11:52:10 -0400 (EDT) Date: Mon, 26 Oct 2026 15:52:09 +0000 From: Kiryl Shutsemau To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Gregory Price , Zi Yan , Joshua Hahn , Rakie Kim , Ying Huang , Johannes Weiner , Vladimir Davydov , Michal Hocko , Hugh Dickins , Baolin Wang , Lukas Czerner , Carlos Maiolino , Christian Brauner , Jan Kara , Daniel Verkamp , Jeff Xu , Muchun Song , Oscar Salvador , David Stevens , "Matthew Wilcox (Oracle)" , William Kucharski , Chris Li , Kairui Song , Nhat Pham , Miaohe Lin , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Mason , stable@vger.kernel.org Subject: Re: [PATCH 04/16] mm/shmem: honour F_SEAL_EXEC when an ACL is set Message-ID: References: <20261026-fixes_shmem-v1-0-703206d5fa0c@kernel.org> <20261026-fixes_shmem-v1-4-703206d5fa0c@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261026-fixes_shmem-v1-4-703206d5fa0c@kernel.org> On Mon, Oct 26, 2026 at 10:40:37AM +0100, David Hildenbrand (Arm) wrote: > From: Chris Mason > > The owner of a memfd sealed with F_SEAL_EXEC can still change its > execute bits by setting a POSIX access ACL. With CONFIG_TMPFS_POSIX_ACL, > this lets an unprivileged owner make a non-executable memfd executable, > bypassing vm.memfd_noexec=2. > > simple_set_acl() updates i_mode directly, bypassing the seal check in > shmem_setattr(). Add shmem_set_acl() to check the resulting mode. Share > the F_SEAL_EXEC check with shmem_setattr() using memfd_check_seals_mode() > in include/linux/memfd.h. > > Fix generated by an LLM and sent by Chris Mason in private. > > Fixes: 6fd7353829ca ("mm/memfd: add F_SEAL_EXEC") > Cc: stable@vger.kernel.org > Signed-off-by: Chris Mason > [ david: use common helper; simplify description ] > Signed-off-by: David Hildenbrand (Arm) Acked-by: Kiryl Shutsemau (Meta) -- Kiryl Shutsemau / Kirill A. Shutemov