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Thu, 02 Apr 2026 20:54:52 -0700 (PDT) From: Qi Tang To: Andrew Morton Cc: Lorenzo Stoakes , David Hildenbrand , Andrei Vagin , Cyrill Gorcunov , Oleg Nesterov , linux-kernel@vger.kernel.org, Qi Tang Subject: Re: [PATCH] prctl: require checkpoint_restore_ns_capable for PR_SET_MM_MAP Date: Fri, 3 Apr 2026 11:54:44 +0800 Message-ID: <20260403035444.19965-1-tpluszz77@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260402104712.111d87b0154260372595cadf@linux-foundation.org> References: <20260402104712.111d87b0154260372595cadf@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Thu, Apr 2, 2026, Andrei Vagin wrote: > A approach is to eliminate CAP_SYS_RESOURCE check but pass all > new values in one bundle, which would allow the kernel to make > more intensive test for sanity of values and same time allow us > to support checkpoint/restore of user namespaces. > > The initial implementation of PR_SET_MM_MAP didn't have the > capability check. This clears up the history. The two paths have different permission models by design, not by accident. On Thu, Apr 2, 2026, Lorenzo Stoakes wrote: > But if it's your process does it really matter? You can > manipulate memory all over the place in your process... I went back and checked each impact I claimed. The SELinux execheap bypass does not work because file_map_prot_check() still enforces PROCESS__EXECMEM on anonymous mappings regardless of start_brk. The procfs paths use access_remote_vm() which safely returns zero for unmapped addresses. auxv only affects the process itself. So yes, it doesn't really matter. I should have verified these claims more carefully before sending the patch. Lesson learned. Please drop this patch. That said, the man page still documents PR_SET_MM as requiring CAP_SYS_RESOURCE, and the individual field path enforces it while the MAP path does not. Might be worth a man-pages fix or a code comment to make the intent explicit, but that's a separate cleanup. Thanks everyone for the thorough discussion. Qi Tang