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a=rsa-sha256; c=relaxed/relaxed; d=tesarici.cz; s=mail; t=1733335474; bh=FX4DK5jBUd2vsaiQ4y/5x3FiboD8Gzi0pXUSJlB7xas=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=BGxwdNEjRV32pwxOQ6LQrWVllld+YXD27kz0U8f1G5wM7UIHEVKV4NXmFqQHURsmj DXeLScPzBbZl3lhtAyLkbREUl+b19LwFIyVPXIPsyjSlCLSD2BAbw/DoRNPW5PcSH0 /oaL4nPsXLl5jR84DYXJ0fhruQ4lJAR7gmiC/RYHdmvDUcFgcC4HfvcqA6Nr17jOPK SmzcMvLm1Po+JAvhuTplzcxtJzT/zOzeRDbpjVEHRXJzUOipicUU8mi0OicMoippuc PX+AqHNQkDDXtNS0aQHLVJmrdAsu63QRHJuNxOR8MYAsalvpqou7OxSkQ9D9XTuaKH o/kKyk0HksBRA== Date: Wed, 4 Dec 2024 19:04:29 +0100 From: Petr =?UTF-8?B?VGVzYcWZw61r?= To: jeffxu@chromium.org Cc: akpm@linux-foundation.org, keescook@chromium.org, jannh@google.com, sroettger@google.com, adhemerval.zanella@linaro.org, ojeda@kernel.org, adobriyan@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jorgelo@chromium.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH v2 1/1] binfmt_elf: mseal address zero Message-ID: <20241204190429.0a18dd22@mordecai.tesarici.cz> In-Reply-To: <20240806214931.2198172-2-jeffxu@google.com> References: <20240806214931.2198172-1-jeffxu@google.com> <20240806214931.2198172-2-jeffxu@google.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-suse-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4AA2212001E X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: eaonyy9k638wo5788ymktq796z3emt3o X-HE-Tag: 1733335456-713151 X-HE-Meta: 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 N90wOtgX JbvtMw/C/EM7buerAdMeEVPLgXVdXrIe3GZPxBoVCA1DBB8w8FTgpHFcZ88I8VsEm1P4nWHmFEfD2Gy6ygw1TIdnKbCZ3Wp8dP5B0a8y6xN2JmjPZbgDcFVnb+/I5ZnQMyMmBJtGBRd4qN6Zi7Lb0a0A5QkEKctgynmsZ847b2TFqDHUpFbbCrbuWmvwtJQYb8gjauSshqEcYiTeWdxBvCD2uMedl2g3XdXm2x5czgSb3JHbub6ffjQz6vdL5LB1qstp3+6Re6Y+6Z4/oq81GrphPONdWbgbJORSJSbkJkvZ4l91vMqV4U67q6g3HUbWIyCQpj7VCiYz05vDyeYr5q8parza2e3vtFgyPf028LW9ReFLgKSLnVha+NY76huP4cgbm95knShs7+V8M207y1XFDVA== 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: List-Subscribe: List-Unsubscribe: On Tue, 6 Aug 2024 21:49:27 +0000 jeffxu@chromium.org wrote: > From: Jeff Xu > > Some legacy SVr4 apps might depend on page on address zero > to be readable, however I can't find a reason that the page > ever becomes writeable, so seal it. > > If there is a compain, we can make this configurable. > > Signed-off-by: Jeff Xu > --- > fs/binfmt_elf.c | 5 +++++ > include/linux/mm.h | 10 ++++++++++ > mm/mseal.c | 2 +- > 3 files changed, 16 insertions(+), 1 deletion(-) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index 19fa49cd9907..f839fa228509 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -1314,6 +1314,11 @@ static int load_elf_binary(struct linux_binprm *bprm) > emulate the SVr4 behavior. Sigh. */ > error = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_EXEC, > MAP_FIXED | MAP_PRIVATE, 0); > + > + retval = do_mseal(0, PAGE_SIZE, 0); > + if (retval) > + pr_warn("pid=%d, couldn't seal address 0, ret=%d.\n", > + task_pid_nr(current), retval); > } > > regs = current_pt_regs(); > diff --git a/include/linux/mm.h b/include/linux/mm.h > index c4b238a20b76..a178c15812eb 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4201,4 +4201,14 @@ void vma_pgtable_walk_end(struct vm_area_struct *vma); > > int reserve_mem_find_by_name(const char *name, phys_addr_t *start, phys_addr_t *size); > > +#ifdef CONFIG_64BIT Strictly speaking, this should be #if defined(CONFIG_64BIT) && defined(CONFIG_MMU) But since we do not support any 64-bit architecture without MMU, I'm just making this marginal note, so it can be found in ML archives if needed. Petr T