From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 46D8F18A6A7 for ; Wed, 8 Apr 2026 12:32:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775651563; cv=none; b=p7En20FxTHmOgo0qKPOc1VAybqaC20Mp8OpHU/kM2q4V08b/CmyKxCOzxy+FUiEShJgaCTbxbzxNYK4zNPek/NdeiTtiiB20eiJFZU4fNZyCuo1mwI+xW8B02gRoHr6ldJ/R37dbW+VXRf2Y/WFnPQwQCAOGkVS0egCtr4ZejMA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775651563; c=relaxed/simple; bh=DB1Krey160BnRiYxuKvyLIZvkNIJjz9VCYiEE5ZLWHo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ImjfvpwBXeuy+HlRLzlzt8Vv9YB6YQqJXeRlvj9w2ILFSWmd356PNCm1CbHKmUUVZU2Qa51kWA0aSQY47DYW/x0nfcQJXNIeIdE6k1hYH3mEPcht6BkeaYzwvlaMeWz126Jt1tVhVEKHTIoO0+Dj764kPYER33ScEJQJ8dcrY+M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R9XjnG5l; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="R9XjnG5l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7EF8EC19421; Wed, 8 Apr 2026 12:32:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775651562; bh=DB1Krey160BnRiYxuKvyLIZvkNIJjz9VCYiEE5ZLWHo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=R9XjnG5lAQDmSxxvrMuZ758QcoPcLqA6ltlEx1m8fPldwxXyGLTefyUnAC5vcbANH hlQ5sZoUF12GF8cqxv3mOA2rNA6OWH5bgjlwUc/Z7t9BtK1ixaupcWy2MqSGLM4OjA JJhOhMfPR0HQH5t5bVpBgvIThWL3UeK1BMUWWNgLZkmpZKOxDeWLsX5la5y32vDz0p 56mkQpsmwUSkgbWKENcpwuFfoT02bL2QKbbkBsb9yEWrqQ2smP3vIubdLzjpLeYXwh 3KbGodWZah7jJk5K6QMbowC6vzO5QuzaLXecXl0FDa9ASw8GhyURGy/Eh+rdszSyXD ZTnH6puMJL+1w== Message-ID: Date: Wed, 8 Apr 2026 14:32:40 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] prctl: require checkpoint_restore_ns_capable for PR_SET_MM_MAP To: Qi Tang , Andrew Morton Cc: Lorenzo Stoakes , Andrei Vagin , Cyrill Gorcunov , Oleg Nesterov , linux-kernel@vger.kernel.org References: <20260402104712.111d87b0154260372595cadf@linux-foundation.org> <20260403035444.19965-1-tpluszz77@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/3/26 05:54, Qi Tang wrote: > 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. Would you have time to improve the man page? :) Also, I think it might be helpful to add some comments in this code *why* it is okay to not do any capability checks. Can you look into that as well? -- Cheers, David